I disagree that it won't command significant value.
Range made PPK/S pistols are preferred over S&W made pistols, in large part because of the annoying beaver tail and some other detail changes S&W made (when they should have left the design alone).
However, with that said if you do indeed have a Ranger made PPK/S that was roll marked as an S&W product, it is an unusual variation - to the point of being rare. There were only 6600 PPK/S pistols in .380 ACP made at the Gadsen plant in 2000 - between the Interarms agreement and the new S&W agreement. It's not clear how many of these 6600 were S&W marked, so 6600 is the outside figure.
The odds are good that it's worth a fair bit more than either an Interarms marked Ranger made PPK/S or an S&W marked PPK/S.