This marking is one of many slight variations in phrasing found embossed in a circular formation on round milkglass liners (“inserts” or “discs”) , part of zinc screw lids used with the “Mason” style canning/ fruit jars.The glass liners helped prevent food from coming in direct contact with the metal lid, which otherwise caused a metallic “off-taste” to be imparted to preserved food (not to mention the increased possibility of contamination from bacteria). Boyd was issued a patent for his invention (#88439) on March 30, 1869.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.
The timeline of markings (which ones came first) is uncertain. The lids 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, shards of glass tableware, etc.Hazel-Atlas Glass Company (after 1902) is known to have produced large quantities of the inserts.Although most of them are found in an opaque, or semi-translucent white milkglass, some are seen in “off” shades of milky or “foggy” aqua, green or blue.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). They are often found separated from the zinc lid they were once a part of.Boyd insert – semi-translucent " data-medium-file="https:// data-large-file="https:// class="alignleft wp-image-1932 size-large" title="Boyd jar lid insert - semi-translucent milkglass" src="https:// alt="Boyd insert - semi-translucent" width="640" height="488" srcset="https:// https:// sizes="(max-width: 640px) 100vw, 640px" / Many slight variations in the exact lettering are seen.