I have had several different bottles of Rittenhouse BIB. The first time I found it was in TN. Later I discovered it occasionally in IN. I can't recall any DSP numbers, but they all tasted the same. As Jeff described, sort of a softer WT rye. It also reminds me a bit of Grandad 114. I have never seen Pikesville in a store.
So far as I know, all of Heaven Hill's rye whiskey is still made by Brown-Forman under contract to HH. That whiskey is strictly made for HH and isn't sold by BF to anyone else. Yes, the Rittenhouse and the Pikesville are the same juice.
The whiskey in the Rittenhouse 21-to-25 year old is rye whiskey made by Heaven Hill at DSP-31.