I cleaned the old HP up and tracked down some info. It's a true Highway Patrolman, not a Model 28. It's a 4 screw. Ser.# S120XXX This dates it to mid 1956 or 1957. Still trying to narrow it down more. The stocks aren't original. They're dated April, 1987. I'll track down an original set with the diamond eventually. It's a great old gun with very little use, as indicated by the light cylinder ring.