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They were continued to be made in huge quantities for many decades thereafter, with production probably extending well into the 1950s or later.
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.
Some of the lids carry mold numbers, such as “2” or “3”.
The mold numbers, especially on older caps, are often hand-engraved and rather crude-looking.
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.