There is no Ferlach code 88. This seems to be code 33, meaning Franz Sodia.
Yes, Ferlach made the older 8x57IR into the middle fifties. Don't be surprised, things moved slowly under the Karawanken :-)
As for IJ and the date I would not know the meaning. But the 16/65 mark I see intact so there was no official chamber lenght change.
BTW many Ferlach guns at the time were ordered by German gunsmiths/gun dealers, and marked so.

Cheers,
Jani