You may be right Fred. PR8 marking is still mystery....I have m43 and m1893 Spanish bayonets with this marks (pr8). For sure they don't fit to FR8 rifles, but perfectly fit to Mauser M98 or M43 rifles. We shouldn't forget about different adapters to allow different bayonet to fit certain rifles ( for example adapter to allow 1941 Bolo bayonet to fit K98 Mauser rifle)
Searching deeper I found more version of this mystery PR8.
- Rework facility - the Servicio de Recuperacion de Materiales de Guerra, which depends PR8: Parque de Recuperacion no. 8.
- Parque Regional No.8 in Mallorca.
This versions bring us back to Spanish civil war , when two institutions for two contenders that needs desperately to get arms: for the Republic, the Subsecretaria de Armamento, for the rebels, the Servicio de Recuperacion.
As a theory - all weapons marked PR belongs to rebels army and explain a huge amount of German K98 bayonets with this marking.

Andrei