“BOYD’S GENUINE PORCELAIN LINED CAP” This marking is one of many slight variations in phrasing embossed on circular milk glass liners (“caps”, “inserts” or “discs”) – part of zinc screw-type lids used with the Mason (screw-threaded) style fruit jars.
The glass liners helped prevent food from coming in direct contact with the metal lid, which otherwise would have caused a metallic “off-taste” imparted to preserved food (not to mention the increased possibility of contamination from bacteria).
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Lewis R. Boyd was issued a patent for his invention (patent #88,439) on March 30, 1869. The actual title of the patent is termed “Improved Mode of Preventing Corrosion In Metallic Caps”.
The patent can be viewed here, a .pdf file from the sha.org site : Boyd’s Patent of March 30, 1869.
Tremendous numbers of these glass discs were made, by a number of glass companies, many of whom are as yet unidentified. Some of the earlier examples may have been produced by Consolidated Fruit Jar Company, and/or Hero Fruit Jar Company.
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Hazel-Atlas Glass Company (after 1902) is known to have produced large quantities of the inserts. A photo of one of these is shown below.
Although most of them are found in an opaque, or semi-translucent white milk glass, some are seen in “off” shades of milky or “foggy” aqua, green or blue. Only a very few of them were actually made of true porcelain, the great majority being made of glass, notwithstanding the phrase which would indicate otherwise.
It is difficult if not impossible to assigned specific years of production to any of these liners. Presumably, the first ones date from approximately 1869. The very earliest versions are said to have been made in transparent glass, with milk glass versions introduced approximately 1871. It is assumed that most of the earlier versions of these liners have the name “BOYD’S” or “BOYD” embossed on them. Later versions may or may not have the name included in the lettering.
The glass liners were continued to be made in huge quantities for many decades thereafter, with production probably extending well into the 1950s or later. The timeline of markings (which ones came first) is uncertain. Many of the metal zinc lids marked “BALL” (in cursive) come with an insert marked “Genuine Zinc Cap for Ball Mason Jars” (no mention of Boyd). Those were made for fruit jars manufactured by Ball Bros. Glass Manufacturing Company.
According to some information presented by “Joe” in this website discussion thread – about Ball jar closures and inserts, the discs marked “Genuine Zinc Cap for Ball Mason Jars” may date from the 1920s, 1930s and 1940s: Ball Zinc Jar Lids Discussion
Some discs are found with spelling errors, as the two shown on this page. One includes the word “PORCELAIN” misspelled “PORELAIN” ; another one is marked “PORCLAIN”. There are probably other error spellings out there to be discovered! I didn’t notice these errors until looking very carefully with a magnifying glass!
The liners are frequently found by bottle diggers at old dump sites, or in privies (where outhouses used to stand) along with other durable (non-degradable) items such as bottles, jars, broken dishes, pottery sherds, porcelain casters/wheels, shards of glass tableware, coins, marbles, toys, metal objects and other artifacts. They are often found separated from the zinc lids they were originally attached to.
Many slight variations in the exact lettering are seen. Some of the lids carry mold numbers, such as “2” or “3”. The mold numbers, especially on older inserts, are often hand-engraved and rather crude-looking.
Here are some of the lettering variations recorded (there are surely many other variants that exist besides these!)
1) Boyd’s Genuine Porcelain Lined Cap [There may or may not be a mold number, such as 1, 2, 3, 7, 9, 13, etc, embossed in the center, or along the rim]
2) Genuine Boyd Cap / For Mason Jars
3) [Diamond logo] Genuine Zinc Cap [Diamond Logo] For Ball Mason Jars
4) Genuine Porcelain Lined Mason Cap
5) [Hazel-Atlas mark in center] Genuine Boyd’s Cap / For Mason Jar / [mold number]
6) [M inside a diamond mark in center] Boyd’s Genuine Porcelain Lined
7) Maltese Cross logo [with letters H F J Co , placed inside the four “arms” in center] – along with the words “Boyd’s Genuine Porcelain Lined”, this type used with lids made for the Hero Fruit Jar Company jars.
8) Maltese Cross logo (in center) with letters in “arms” as above, and the words “THE HERO FRUIT JAR COMPANY / PHILA. PA.” in circular formation around the rim (shown below).
9) Unmarked – No numbers or letters.
10) No lettering, except for 3 concentric raised lines (rings) and a mold number in center. Mold numbers may be two digits such as “33” or “64”. I am sure there are many other numbers out there! I’ve seen these discs inside zinc lids marked with the “BALL in cursive” logo on top of the lid.
11) Mold number only, no concentric rings, no other markings.
12) Consolidated Fruit Jar Company – New York (C F J Co monogram in center)
13) Boyd’s Genuine Porclain Lined Cap – [Number] (note “Porclain” misspelling)
14) Boyd’s Genuine Porelain Lined Cap – [small sideways number/larger Number/small sideways number] (note “Porelain” misspelling)
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[Added January 24, 2020] Below I am posting photos of an unusual “bulbous” disc seen with the markings “APRIL 2ND 1895” and “PAT. MAY 28TH 1895”. These “immerser lids” were made to accompany certain jars made by Gilchrist Jar Company. (Some jars or discs may have been made by Hazel-Atlas Glass Company). These pics were sent to me by Stacy Rawlings. THANK YOU Stacy! More background info on these jars and the lids can be found at this pdf file article by Bill Lockhart et al: Gilchrist Jar Company
For more information on some of the types of fruit jars involved with the Boyd inserts, see these webpages on the Ball Perfect Mason, and MASON’S PATENT NOV 30TH 1858 Fruit jars.
For an extensive alphabetical list of marks seen on glass bottles, fruit jars, electrical insulators and tableware, please click here to go to the Glass Bottle Marks pages (page one).
Click here for my website Home Page.
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I found one fishing in the Cuyahoga River in Cleveland, Oh….BOYD’S GENUINE PORCELAIN LINED CAP 300…GARY TOMOTCHKO
I have found several clear glass inserts, a few have presto and a few have the word Harvest. I would appreciate any info.
Just found a Boyd’s Genuine Porcelain Lined Cap. Mine has a distinct 5 in the middle.
I found one too! Digging next to the foundation of my 200 yr old house for post holes. So I was a good bit down, house was built in 1887. It says boyds genuine porcelain – but spelled wrong – cap, and there is a #1 in the middle of the circles!
Found one today with Boyd’s Genuine Porcelain Lined Cap at the American Fall’s, Idaho river they are draining. It was where the old town was before they moved it. Really cool find.
I found one Wednesday Nov 9th while metal detecting a small park in north Idaho. It’s milk glass says Boyd’s genuine porcelain lined cap, no other markings … cool find though was thinking jar full of old gold and silver below it but NOT…
Hi Richard,
Thanks for your post!! Hard to know exactly why the cap was there, but maybe someone had brought a Mason jar with some kind of beverage in it to a picnic (many years ago) and the lid was thrown away or lost. Or there used to be a casual dumpsite in that area?
That’s definitely a better find than a nail, a bottle cap or an aluminum pull tab!
Take care,
David
I found one in an old cellar of an old house from the 1950s at least.
I found four in a creek down by my house
I found one today while metal detecting with my XP Deus 1 about 9” deep. Luckily part of the zinc screw on lid was on it, I’m so glad I didn’t hit it with my shovel. I found it behind my house here in Bokoshe Oklahoma.
Archaeologist here, working on a collection of artifacts from Knoxville, TN. Just ran across some wording on a Boyd’s liner: “BOYD’S GENUINE PORCELAIN LINED” with no use of the word “CAP.” It is made of translucent white milk glass.
CFH,
Thank you very much for the info. I am assuming the liner you found does NOT have the “M inside a diamond” in the center, correct? I’m only asking that because of one of the variants noted in my list on the page. I want to make sure the one you are documenting is definitely another variant.
Take care,
David
I just found a Boyd’s cap in upstate New York. Originally I thought that it was a cap to a small white jar that I dug up next to it but it wasn’t a clear fit. The jar still had some sort of paste in it! Pretty cool to now know what the white disks purpose was. Thank you
Hi Brianna,
Thanks for your post! Those Boyd’s discs can show up just about anywhere! Take care,
David
I dug up a Boyd’s lid with 25 8 and a cockeyed H on the rim of the porcelain.
It has all of the usual words. “Boyd’s Genuine Porcelain Lined Cap” and then those that I mentioned.
Any idea on this one???
I found one with a 24 instead of 25. Wish I knew more.
Tom, many different mold numbers are found on the Boyd’s milk glass liners. The mold numbers don’t “mean anything” other than identifying the mold a particular liner was produced from. The molds were engraved with different numbers to identify each one, and to easily pinpoint the specific mold if there were any problems with the finished glass product coming from that mold (in this case – jar liners).
Best regards,
David
I found one of these little kiddie dishes on the surface of an area I suspected to be a dumping ground back in the late 1800s. It says “The Hero Fruit Jar Company Phila Pa” with the Maltese cross in the center. Thanks to this page I know what I have.
Hi Ed,
Thank you for your post! Your “kiddie dish” quote made me think that it’s very possible some of these have been used, at some time or other in the past, as miniature plates or saucers – by girls playing with their dollhouses!
~ David
Thank you! I found one of these when sea glass hunting in Maine. It’s only slightly damaged and is a fun piece to have, especially now that I know what it was used for!