The earliest version has two c clips and no markings. The bipod legs are slightly wider than the others.
The C clip designs were a problem as the clips always break lose. I have the one c clip version and it is loose. I am getting it repaired.
Another characteristic of Colt bipods is the rust. Where the welds were located, the ingredient they used to pre weld created a lot of rust because it was not cleaned off. I have seen the rust on probably 50% of all Colts I have inspected.
If I recall the earlier C clips were bright, not parkerized.