That is quite a find!

Every once in a while something fortunate like that happens, like when I purchased a 19" Apo-Artar and it turned out to have the same flange as my 12" Gold Dot Dagor of later vintage, so I could mount them with the same S. K. Grimes adapter ring on the front of my Ilex #5 shutter from my 10" WF Ektar (a very compact way to carry 3 lenses for my 8x10" kit), and then later when I got the 5x7" Press Graflex, the stock B&L 5x8" Tessar could take the same flange, so that lens works on the Ilex #5 and the Dagor works on the Press Graflex, but alas, the Graflex doesn't have enough bellows for the 19" Artar.

Another nice one was when I bought an estate lot for a Sinar F with a lot of accessories, one of which was a 4" gel holder that fits the 10" WF Ektar. The finish on the metal looks the same as the Ektar, so I suspect it's an original accessory.