The seat tube top looks like someone at some point had a stuck / sticking post and decided to open up the top of the tube in an attempt to free it with a screwdriver.
Its not round and the edges were all chewed up and rather sharp.....all ive done is file off the bad bits so far as to allow a nice post to go in without damage, for testing.
Plan is to put big washers on a bolt through the clamp, heat up the tube top nice and hot and clamp it round an old post to straighten it up.....then re dress the top edge and the slit/ clamp....which I have no doubt will have been stretched....
I think it was Vyvyan's metal hamster
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