Background: I have a spare frame that I bought a couple of years ago. Engine mounts had been modified to fit a different motor but along the conversion the owner got tired and sold off the frame (frame, subframe, swingarm and shock). A while ago I decided to take out the rear shock from my bike to renovate it and at the same time switch the swingarms from the spare frame (my original swingarm is missing one bobbin lug and has a few scratches from a chain that broke).

Today, when comparing the two swingarms I could se that they differed in several ways. Are these hand made modifications or is there a very similar swing arm that someone fitted? What do you think?

My original swingarm to the left, the spare to the right.

Is it possible that someone has gone to the length of removing the rear brake mounting slide thingy on the inside of the swingarm and leave almost no trace of it? Why not just leave it since it is not showing, beats me.
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MC21, GP-Replica (Daijiro Kato, Telefonica Movistar Team 2001)