From everything I read about them, the TTL prefix on the serial number on the Century Tantals were the ones that had the keyhole issue. The previous owner on mine had tested it and confirmed it had the keyhole issue. I sent it out to a builder for barrel replacement right away. Century was aware of the problem, using a 223 barrel, chambered to 545 from what I understand.
shoot it and see if it key holes, worst case if you are getting a killer deal can get barrel and builder to replace for 250-350ish or might be best to pay more for the many listed on sites and be done with it