This is an unusual one. There have evidently been two different Model 520s offered by Smith & Wesson.
The first was an "N" frame revolver, basically a Model 28 with fixed sights. I think they were made specially for NYPD beginning in 1980.
The second one was more recent, but I don't know the timeline. I believe it is or was basically a Model 586 Plus, without the full underbarrel lug.
If I have ever seen one or the other, I wasn't aware of it at the time.
Which one does your buddy have?
It's not that liberals are not smart, it's just that so much of what they know isn't so.