That is the first blue one I've seen! I also know of a stainless KBP-5, Ruger model 1409), serial number 145-90688 which would have had a production date of two years before the fixed sight 5-1/2" guns even came out! That is, if 145-90688 was made then.
The BP5 in the thread is Ruger model 1410, serial number 145-95350 and it would appear to be one of the cleanup guns as it has red laminate grips with silver medallions that have a black background.
Rare guns indeed! Now if we can only figure out why Ruger made these, or maybe a distributor did a small run in blue and stainless? The wide gap in serial numbering has me a bit perplexed, and it would have been no small matter to have a wax injection die special made for the shorter than normal loading lever.
Looks like the Warning address is also on the left side of the barrel.
Chet15