Introduced: 1983 (second run in 1988)
Hallmark/Samhongsa released all of these various GP7/9 models at the same time (1983), and presumably they all have the same basic chassis/mechanism. So I'm going to save myself a bit of time (not to mention money) and review them all here (based on the couple of models I've actually purchased and tried out).
As is generally the case with brass, these models are all gorgeous. Unfortunately, they do lack window glazing, headlights, couplers and number boards (also generally the case with brass, or so it seems).
Reviewing the performance on these models is a bit tricky. The mechanisms (featuring all-wheel pickup and a 5-pole motor) no doubt ran pretty well back in the day. Good slow-speed creepability, reasonable top-end, smooth throttle response, no problems with narrow-radius curves, etc. Maybe a bit louder than we'd like to see nowadays, but respectable. And yeah, all of those wires running around are a problem waiting to happen, but come on, we're talking 1983.
Unfortunately, these models have not aged well at all - this due to the plastic gears inside of the truck towers. Whatever plastic Samhongsa used way-back-then turns out to have been prone to shrinking and/or cracking. And the end-result (in the 21st century) is a lot of locomotives that spin their motors and driveshafts quite well, but with none of that motorized enthusiasm making it to the trucks. And beware - adding any sort of lubrication into the mix at this point will only makes things worse. The two Geeps I've actually tried out ran OK for a while, but eventually became basket cases. No doubt about it, the stress of operations will ultimately reveal the deterioration of those plastic gears - at which point said Geeps will become very noisy and very parked.
So, I suppose if you could time-travel back to 1983 and purchase one of these new, it might run at a "B" level. Unfortunately, based on my experiences they seem to be performing at "F" levels these days. Then again, replacement gears are an option (if you can find them), so I guess I'll split the difference and give them an overall "C" rating.
Notes and trivia-
All of the non-passenger units have removable dynamic brake blisters (they actually came as an ala-carte add-on in the "spare parts" package for undecorated units).
I've noticed that some of these have brass driveshafts while others have plastic ones. I'm assuming this is a variation between the two runs (1983 and 1988), with the second run probably having the plastic driveshafts. I didn't notice any appreciable difference in performance between the two versions.
To remove the shell, unscrew the two small screws on either side of the fuel tank. The shell should pull right off at that point.
Beware trying to work on the trucks. Yeah, the gears are all easy enough to get at - just remove the three screws from the bottom of a given truck. Unfortunately, this will cause the entire assembly to fall apart into a million different pieces. And just try to get everything put back together correctly - it takes more hands than human beings were born with!
Be very careful with the screw that connects the two halves of the truck towers (and runs through the dreaded plastic gear). The threaded end is awfully short and prone to stripping.
If you're looking for replacement gears, NWSL may be able to hook you up. I replaced the worn out plastic gears in my GP7 with part "1074-6 23 Tooth Gears" and was able to get it running again.
Torpedo tube (passenger) versions were also available-
"B" units were also available (based on my eBay experiences, these are much harder to find than the "A" units):
Grade: C ("B" with the truck tower gears replaced)