Does my Russian SKS have a chrome lined barrel?

[ciphery]

It would have to be pretty thick chrome to defeat a magnet.

Put some gun bluing on a q-tip swab and a dab to the bore. Chrome won't blue, but bare steel will.

The bluing idea will work. BUT. I disagree with your magnet theory. I'm a chrome plater by trade eh!

 

[ciphery]

Sometimes they grind off the existing serial numbers and restamp -correct?

Correct....sometimes and sometimes they just peen/scratch,###,---, through the old numbers and stamp new clear ones underneath or beside them.

A ground and restamped part is usually referred to as a 'force matched part'

 

[svt1940]

Sometimes they grind off the existing serial numbers and restamp -correct?

Yes can happen, everything is possible with refurbishing.
Jocelyn