Hello Takashi,
Good looking watch.
I agree there are not alot of time only DR pieces from that era that are manual wind. Most of the manual wind pieces were
tourbillon, or had complication modules attached to them (perpetual calendar). I dont think this impacts value though. As for calibers used.....DR used FP, Lemania and others that were refinished or reworked as you put it.
I have not heard of any issues in regards to the time only watches from DR. Usually the complication pieces had issues such as the Perpetual Calendar equation of time. This was due to user error when setting most of the time.
As for servicing.....it would go back to Bulgari for any repairs or service. This isnt a problem as Bulgari has owned DR and GG for 13 years now.
Question: I cant tell from the pics but did the seller edit/remove any gold markings from the case or engravings?
-KHD.