The Mitutoyo parts list for DRO/Counter unit stuff shows this manual as p/n 29624
The DRO unit is a white/beige box with grey front panel, 2 axis, green digits, membrane keypad shown here..
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I think this unit was manufactured in 1991 or 92 The full model number is something like APL 164-6xx but the digits are wiped off the label.Remove the X from my reply to address to contact me, I'm in the U.S.
Thanks WB