I have "B" code rear springs on my F250. They have an ink stamp with YC35-5560-CA and metal stamp YC35-CA and RPN 2800. They are F350 SRW springs. They were not original to my truck (per Ford build sheet for my VIN), but were already on it when I bought it.
This link may help also. https://www.ford-trucks.com/forums/1...spring-id.html It does mention the number you have.