When I commented earlier, I totally misunderstood the question. Sorry.
The buttonholer that I bought with my T&S is part number 381116. It is labeled Singer Professional Buttonholer. It came with plate #383013. The 383013 has no part number engraved on it. I assume it's the 383013 because I've had the buttonholer since it was new and it's still in the original box.The box says it's "for use on 700, 900 and 2000 series machines. For 401 500 600 620 and 640 machines use part 161825"
The buttonholer I bought a few months ago with a 503 is labeled, Professional Buttonholer by Singer. It is part 161829. It has no description of what machines it fits other than Slant Needle Zig Zag sewing machines.
I have a Singer Monogrammer for slant needle zig-zag machines that appears to be similar to a buttonholer. I bought it in an estate sale. It says, "accessory plate 161825 furnished is for use on 401 500 620 630 and 640 series machines. For 700 series machines use, 507661."
The photo below shows the 3 plates. The 161825s little "barbs" are almost flat. The 507661 stick up higher with the one on the right in the photo sticks up even higher. On the 383013 plate, both barbs stick up equally high.
The bobbin that is bigger on one side is probably a bobbin for a Touch and Sew. If it doesn't have a real hole in it and unscrews/comes apart, that's what it is.
The plate you show in your first post appears to be the buttonholer plate for the older Singers like the 15-91 and 201s.
bkay
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