T3 Headlight-different numbers embossed in glass?

[68camaroz28]

Was looking at the T3 headlights still in their buckets on our 68 Z/28 and noticed at the top there is what appears to be a lower case L followed by a # series. Each of the two originals are different with a l91 and l114,  and two NOS ones I have have different numbers as well but also use the lower case L. One person thought that was a mold number. Seems logical but trying to verify what they are. Have not taken them out to see if the stenciled date code is still on the back half.

[68camaroz28]

Per JohnZ- it's a Guide Lamp mold number - they made about 60,000 lamps every day, so there were multiple mold cavities.