Product Details:

Gear Box for 55-111BRS, 55-111BC, 55-111CP Handle Set Assembly for Swing Door.

Manufactured by Roto.

Backset: 1-3/8" (35mm).

If replacing an Old Style Gear Box (see the two listed as obsolete in the picture above) with the New Style Gear Box (56-106 or 56-105) the door will need to be notched out 23/32" to accept the position of the New Style Gear Box.  Also, the Strike Plate 12-313PB or 12-314PB will need to be lowered 23/32" to line up properly with the Latch and Dead Bolt on the New Style Gear Box.