Just a bit of clarification: The picture posted by the OP, is NOT a PREMIER model. It is one of the many variants of the "AUTO EJECTING" model. From the picture it is a later - late 1920's to early 1930's variation - stamped and catalogued as the "H&R AUTOMATIC". The Premier is the small frame auto ejector. It was chambered for 7 rounds of .22 s or long (after about 1930 it would also take .22 lr) and 5 rounds of .32 S&W (the short one) ONLY, through out it's life span. The Auto Ejecting Model was the large frame and would handle 6 rounds of .32 S&W, .32 H&R Long or .32 S&W LONG, depending upon year of manufacture, 1904 and earlier were black powder ONLY. The PREMIER mentioned above with the non-stepped grip frame is the last variation and with the serial number in the 500K range it was most likely made in the early to mid 1930s.
All H&R revolvers of these types were offered with Nickel finish or Blued. Earliest ones, pre-1920's or so, seem to be predominantly Nickel plated - with blued finished pieces becoming more prevalent after that date. In the 1930's, the majority seem to have been made with blued finishes.
The letter codes and dates which Bossloper listed above, is the result of research done by Bill Goforth and me, and at this time seems to fit with catalogue listings and known changes exhibited by pieces in my H&R collection.
Any questions, please ask.
Jim Hauff, H&R Collector
Contributing Editor for H&R firearms to "THE BLUE BOOK OF GUN VALUES" by S. Fjestad