Cylinder mold number?

[drh]

In comparing two copies of Edison Blue Amberol 28115, Carlo Galeffi singing "Il Provenza il Mar" from Verdi's La Traviata, I saw something I'd never noticed before: the cylinder catalogue number and a further figure hand-engraved into the deadwax at the title end. One copy has 28115-3; the other 28115-4. Are the hyphenated digits mold numbers? Or do they indicate alternate takes, like the A, B, C, etc. designations of Edison discs? Photos below.

[gramophoneshane]

I can see 28115-4 also says 4 on the title end, so I'd assume if 28115-3 also says 3 on the title end then they are mould numbers.

[gramophoneshane]

Definitely mould numbers.
Just checked a couple of mine, and they all match the title end mould numbers, like 1570-44 for example.