Jon Swindle and I spent an afternoon late last year measuring 20+ Prussian Dalys and other Lindner guns. I was not focussed on it, but Jon was smart enough to take note of whether the lumps pierced the action body. What we found was a pretty narrow serial number range where the change appears to take place. I say "appears" as it seems there is always an exception to absolutes in researching Prussian Dalys.
What we noted was that change takes place between serial #683 and #705 - i.e., guns below serial #683 did not have the lump showing and those after #705 did. Given these serial numbers, the transition would have taken place circa-1896.
It is important to note that I'm referring to second set of Daly serial numbers here - i.e., the series of serial numbers associated primarily with Lindner and marked with the "HAL" over crossed pistols markings, not the earlier guns.
Given the realities of making the guns, I would doubt that the break can narrowed to a specific serial number, but I would suspect the range identified above will be pretty close. Again, I am sure there are exceptions.
Hopefully this is helpful.
Ken
