My P-15 has a unicanitor saddle. I got it from the original owner in 1980, with about 150 miles on it.
In my opinion, schwinn offered only 2 types of saddles on the original 1970's paramounts - - -
1. Temporarily hard. A Brooks Professional.
2. Permanently hard. Unicanitor. They NEVER break in !!!
- Don Gillies
San Diego, CA, USA