I'm not sure if this can be done ,but I would like to repair this Case Gin. I think it is rather old being footed and having a polished pontil. I would apricate any leads to someone with the expertise to fix this. Thanks
Art glass may have a ground pontil scar, but not utility bottles like this one.
Repairs like this would require might be done with casting resin or colorless 5-minute epoxy. You can try to match the glass color using dry powder pigment or scrapings from an art crayon (not the wax) -- visit an art supply store for these.
Build a dam with modelling clay. Fill with resin. Remove the dam while the resin is not totally cured (stlll slightly pliable), and use your Xacto knife to trim excess resin (gently, till the patch is close to what you want). Let the resin cure, then sand the patch to match the lip. Once you have a good match, you can apply a thin coat of resin (don't bother to tint this coat) to the sanded surface to restore gloss. The gloss coat may cover minor carving errors.
If you're not happy with the results, the cured resin is not difficult to remove. Snap the patch off and start over. Let us know how it goes, even if it goes poorly.
Nhpharm gives pragmatic advice. I assumed that otto has some personal reason to want to restore the lip.
This is a late bottle, much later than the era of pontil scars. The bottoms of such bottles often have enigmatic mold marks, but these are not pontil scars or ground pontil scars. Though late, these hand-finished bottles may have lots of character.