Looks like I am late to the thread . . .
First off, that is a very well-bought Prussian Daly. Nicely done! As has been mentioned, featherweight Dalys (i.e, Dalys marked as such on the rib, not just lightweight Dalys) are fairly rare, and especially those with 28" barrels (26" is more common).
My best estimate on the production date of your gun is 1900 (+/- one year). The model number is a bit tricky as I don't own a 1900 period Schoverling, Daly, and Gales (SD&G) catalog. That said, I think it is most likely a 155. My hesitation here is that the Daly model numbering sequence was in a bit of flux during this period. Said more simply, I know what the model numbers are (per period catalogs) prior to your gun's production date and after your gun's production date, but I don't have the data in the middle. And because the model numbers in the catalogs I do have are different, I'm hesitant to state anything definitive on this gun. That all said, I agree with Canvasback and think it is a 155. (The presence of ejectors and cross bolt fastener are key features to help with the grade.)
I think this gun will clean up really nicely - congratulations.
Ken
