I have a number of small white pills that are imprinted with SP on one side and 141 on the other. I know that they are Diphenoxylate HC1 2.5mg (fortunately I still have the original bottle because no where online was I able to find a pill fitting this description)

I also know that this particular pill was prescribed by the VA in 1991, which has their own pharmaceutical department and uses it's own identification markings unlike those found on pills typically gotten from the drugstore (which is most likely why I was unable to find this pill online).

Putting aside the fact that the pills are definitely expired, I am wondering when atropine was introduced as an abuse deterrent? Have Diphenoxylate and atropine always been prescribed together? or could these pills possibly have been made before atropine became a standard additive to diphenoxylate?