Got a used crank but most chainrings don't fit on it.

I thought this was kind of weird so here goes. I got a used 170mm
Shimano Tiagra double crankset to experiment with different crankarm
lengths. It had 53/39 chainrings on it and attempted to mount a 48
chainring that I have been using on another bike. But the chainring
would not fit on the right crank. I tried a couple of other chainrings
and they didn't fit either. The edge of the crank extends too far by
about half a mm where the chainrings mount. Has anyone else
encountered this? Is this the usual with Tiagra- did they make some
other standard 130 BCD chainring with a different chainring inner edge
diameter? Or is this just a bad sample?