It was made between 1952 and 1973.
With no patent number reference, it is generally considered to be post-1952. Some variance here based on some unknown model criteria.
With "Boulder Colo", it is pre-1973ish. The reference to Boulder was dropped in late 1972 or early 1973, depending on the model.
Need a little more information = and a few more pictures would be great. If there is no model number, I can still tell you what the model is based on a picture of the overall knife and a blade measurement.
Is there a model number stamped into the pile side ricasso (the opposite side from what your picture shows)? Yes or No
Is there a model number stamped into the brass guard? Yes or No.
If the answer to both questions is NO, the the knife was made between 1952 and 1955, most likely.
If the answer to both questions is YES, then you have a fake.
Or is is a Frankenknife, assembled with bade and guard from 2 separate knives. I almost did that once when I was working on replacing the leather washers on some old knives that had been abused.
I caught my error before I replaced any pommels, though. Learned NOT to work on more than 1 knife at a time from that incident.