Yep, that head is missing whats called a “sled”. The little arm moves a lock like piece that pulls the sled up and into the head. Heres my 1229 with the same arrangement:
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It’s a “Dual” thing.
Looks like someone has somehow bodged it onto the headshell without the sled. Thats why the locking arm isn’t doing anything.
Unfortunately, you’ll have to figure out how that cartridge is secured to the head shell before it can be removed.
I don’t see anything obvious like through screws in the headshell, so its anyones guess how its in there.
There perhaps might be something that looks like a “cut down” sled in there or a home made sort of sled. Looks like something under the lever. But if its home made, it might not be releasing with the lever or perhaps the lever has been broken somehow and won’t release it.
I’d say you’re just going to have to “poke around” until you find out how the cart is in there…