I'm one of the ones that has started collecting Pedersens.... I've got a 1000... so far
Pedersen Custom Gun was in business from '73 to '75, the side by sides didn't sell as well, so they were only available in '73 & '74.
Pedersen was a completely seperate business from Mossberg, although they were only seperated by an empty lot....
As stated above the 1500 (O/U) & 2500 (SxS) were both imported by Pedersen from Aramberri, perhaps you have a very early model and they hadn't figured out the brand numbers yet??
I recently looked at a model 2500, that was being listed as a model 2000 (he fixed the listing after I checked out the gun), it looked great but had two hairline cracks in the stock, he's now asking $795....http://www.usgunexchange.com/products.c ... =34&ID=897
The "holy grail" is the model 2000, these were imported from Beretta (GR-4), I've still yet to find one of these in person.