I also would like to know how many of these were made. I'm not a fan of porting but I bought this -4 after PowerPorts were discontinued in case they become collector items. It turned out to be unfired and it remains that way.
While I've never shot a .357 PowerPort, I did own a 6-1/2" 629 Classic PowerPort and compared to my non-PowerPort 629 Classic with the same barrel length, the only difference I could see in shooting them with the same ammo was slightly less muzzle jump but significantly more debris in the face with the PowerPort gun.
I don't recommend shooting one with the air moving toward you.
Since I'm new here, it may take some time to post a photo of it. I bought it to replace an earlier 686 that was stolen. Thanks for letting me know that it is a limited edition 686.
The product code on these was 104272, and that was used with -4's and -5's. Possibly other dashes, I don't know. They were made, at least, from 1994 to 2000, so I think there are a good number out there.