I only collect Italian Walker oddities with "close but no cigar" Colt roll marks from the 1970s made before the 2nd gen guns. The Italian repro Walker flasks I have are not stamped made in Italy nor do they have Colt's Patent on the bullet cover nor on the banner on the flask. I believe the 2nd gen Colt flasks did.
Care to share how the local pd evidence locker folks were involved. Were you burgerlized? If so that is terrible, if the evidence guys switched out your Colt flask with a repro, thats near as bad. Did you check the serial number on the Walker that you got back from the property room? From the 1847 mark it does appear to be a 2nd gen Walker.