Sperry Mark 1B DG Overhaul or Exchange Help

[astixjr]

Need some help finding an exchange or overhaul service for the front cockpit Sperry DG Mark 1B in our SNJ-5. The DG is marked "Store Reference No. 6A/1666" and it's dated 1945. I assume that's a Navy stock number. It's having a little problem holding a heading unless you lock it. I guess that makes it a bit useless for navigation. Anyone have a source? Thanks,

[ausflyboy]

6A is an RAF Stock number

[astixjr]

Thanks Ausflyboy. I was wondering about "Mk" designation on this DG. I know the Navy used the "Mk" term for gunsights but I've never seen it on an instrument from the WWII period. At least I've never noticed it. I've been told that this is the same DG that was later called the AN 5735. I checked the one in the back seat and indeed it has the AN 5735 number. I wonder if the front DG is from a RCAF Harvard? I guess this is a case for an "Instrument Anorak".