it's the small metal disk commonly found on the tops of wine bottles with corks mostly on Champagne bottles i think it keeps the wire from digging into the cork!
Bordeaux is also a region of France possibly where J. Delmas & Co were based. "La renommee Transatlantique" means "Transatlantic Fame." Unfortunately, there's nothing on the seal that definitively relates it to wine.
I was contemplating the publishing company possibility too, as the angel with a horn is often meant to portay Gabriel "the messenger" (communicator). As such it's often used by libraries to "brand" their books as well as by all types of communication companies in their logo. So I think that direction seems possible... Maybe to tag crates of books being shipped
I was thinking it's a relief off a binder or case for a set of books. Don't know if this one is metal but it gives you an idea...
The relic may be older than mid 20th C. I saw a few references to J. Delmas Imprimerie (publisher) going back to the 1850's but the bulk of publishing was done 1960 - 1980.