How can I tell if the barrel  on my Tantal is the original polish barrel ? My Tantal  Was built by Interarms on a DCI lower receiver sn# T0059X.  The rifle was built on a matching kit. All the upper receiver parts have matching sn#. Were the barrels on the Polish marked? If so how were they marked? I haven't been able to find any markings on the barrel.

From my knowledge older interarms builders used original polish barrels that werent chromeline, but great barrels!  Newer builds should have chromelined barrels.  The main thing about these is making sure it doesnt keyhole on paper

Thread with barrle markings

Stay away from century arm ones. Mine keyholes like crazy.

Hopefully this isn’t terrible thread necromancy, but here in 2019 you don’t gotta live with that anymore. There are good US barrels now that will solve the keyholing, though the price/effort of rebarreling is not insignificant these days.

AK-Builder CHF chrome-lined Tantal barrel
AK-Builder CHF nitrided Tantal barrel

I just finished populating a Green Mountain Tantal barrel with a matching numbers kit that has been on hold for years. The build went very well with all journals diameters matching the parts. I did have polish off the black finish to get the gas block to press on, but that was all.

There is still one more kit to build, the barrel is a duplicate Green Mountain barrel,  so there shouldn't be an issue. I will report back as to how it shoots, but other builds shoot well with the same barrel.

To answer your question, the Polish barrels are proof marked with inspectors stamps. US barrels are just manufactured & sold blank.