Hey...Wow! Look at those pictures that starcain posted.
First I apologize for hijacking this post but sometimes I can't help myself.
But that rear muffler clamp has two bolts, one to tighten the clamp on the muffler and the other to connect the clamp to the support tube. The one that attaches to the support tube is at 45 degrees (???) to the bolts that fasten the tube to the frame. This is the only tube with that arrangement that I know of. This can be clearly seen in both pictures; one from each side. None of these parts (tube and muffler rear clamp) are depicted in the 1953 parts books. So when the '53 parts book was issued on October 15 1952 (at the beginning of the '53 model year) this arrangement was already replaced with the two hole support tube that we have all come to know and love. That is the two hole tube where both the muffler and the muffler front clamp are attached to the tube in the same plain as the support tube to the frame (90 degrees). So I might "speculate" that the support tube and the two bolt rear muffler clamp were '52 only or part year '52 but definitely not '53 due to the date of the '53 parts book.
Looking back on the picture that Jerry posted of the September '53 K we can see that the visible bolt on the rear muffler clamp does not line up with the tube. The second bolt (not seen in that picture) from below to the tube explains why this appears that way in Jerry's picture.
Also note the stand-off between the muffler clamp and the support tube. Is that part of the support tube or is it a separate spacer. It kind of looks like the spacer between the frame and the support tube. If so it is part of the support tube. Could be...maybe??? More questions......No answers...my apologies...but only starcain's pictures to go from. Maybe EKHKHK56 can look at his original paint '52 and let us know and also where in the serial number line-up it is in the '52 model year.
Thanks and Happy New Year to all
Dave
Dave