Quick IBM Model F Question

[tatsurou]

Hello,
I realised that all XT barrels have different letters on them.
Is that an assembly order perhaps? Or maybe something else?
I am not sure here

[ag36]

Likely markings to identify the mold for QA reasons.

[orihalcon]

Yep, agree, if they start noticing defects in some of the barrels, they know which mold made it and know which one to upgrade/replace.

[tatsurou]

Thanks guys!