The program called for rebuilt M1s to be sent, including WRA and rebuilt former Gas Traps, with only a small percentage of new SA production (3% IIRC). In practice, it turned out to be easier to just ship new guns from SA and so most LLs were new. A verifiable LL rebuild is scarce.
The problem we have is that it's hard to tell an LL rebuild from a regular rebuild unless it is marked in the barrel date area as IMO Sam Cummings specified on the original lot. Of course, it is much harder to mark there than simply on top of the barrel, but he knew collectors would hate the proofs and wanted them in as inconspicuous location as possible.
Interarms was unwilling to provide any information on the imports, despite what I thought was heavy pressure from my end about 1979. I got a response from John Ring, the Sales Manager saying, "You know as much about the arms business as I know about the stock market." LOL