TLR close-up lens

I think that Bay 1 (a.k.a., B30) filters are usually non-threaded drop-ins and are 30mm in diameter. I assume a close-up lens could also be 30mm drop-in. However... if it's 28.5 and branded Yashica, it's likely a Yashica 44A push-on filter/lens. 28.5mm isn't the right size to be a Series accessory (i.e., Series IV hood, or Series VII filter), and too small to be a Leica L39 or A36 drop-in/push-on.

From the images, it looks almost exactly like those shown on Paul's page I linked to... about half way down in the section titled "Filters". The lower black collar is a compression-fit push-on adapter, and the upper chrome lens section is a Bay 1 bayonet mount. I presume that Yashica made these for the 44A TLR's with the included adapters so they could make use of their existing Bay 1 filters/lenses/hoods and not have to create a whole new line in another size. Essentially these could be 2-in-1 accessories that can be used on the budget 44A and any Bay 1 compatible camera.

You're welcome ... but in this case a little knowledge, and a lot of search engine.