Old supplementary links "Day/Date" for watch straps that i´ve never seen-How about you ?

I have seen a lot of watches lately, but I have not come across these supplement links.

They would be ideal for older leather straps, but the selling price puts me off, as does the 16mm lug width.

Vintage Art Deco Kopit Perpetual Kalender Datum Uhrenarmband Ösen Befestigung 16mm | eBay

Does anyone have more detailed information about the manufacturer or even own such links ?

For the archive: