center circles are hotstamps and not slugs.

Only my opinion, feel free to castrate me

1. In looking at potential fixed chips for xray and studying older items Allan had xrayed/peeled in the past, looks like weight slugs were 'dropped in the hole' afterwards. Consequently they are not a tight fit and would fall out if it weren't for the inlay and glue.

Not convinced? Try this one

2. Look at the black chip. Hot stamp is well off center towards bottom. The circle has moved with it Circle must be part of the same h/s die.