FX-1 What do these case markings mean?

[kawa js550]

Anyone have any idea what these case markings could mean? Definitely not factory. Maybe to show the cases are matching set? It says “IG 239” on the upper and lower cases.

 

[Jr.]

Yes, they are factory. They are match marks for when they were line bored
To indicate matching halves.


Ski ya, Paul