The first-generaton GuardLogix Safety Partner for use with the 1756-L6xS series of GuardLogix CPUs had the part number "1756-LSP". The front side plastic was labeled "Logix55LSP".
Because the Safety Partner only runs the Safety Task, they didn't have different memory sizes. One part number would work with any GuardLogix CPU.
The generation that works with the 1756-L7 GuardLogix has the part number 1756-L7SP.
You are correct that there was never a (publicly released) GuardLogix system built on the L1 or L55 generation hardware.