You've probably already seen this over on the 16 ga forum, but for those who are unfamiliar with the Marlin 90 here's a little summary of what I've learned from Charles and other posters on the various shotgun boards:
The best kept non-secret in a classic American OU is the Marlin Model 90. Made by an icon of American firearms manufacturing and brilliant in it's simplicity, durability and handling characteristics. I have a 12,16 & 20 ga and I'd love to find a 410 and a rifle/shotgun combo.
You can still find clean 12 ga model 90's for around $300-$400 but the smaller gauges are bringing double that.
To my knowledge the Model 90 is the only American built OU available in 16 ga.
My primary Clay target gun is a 30" barreled 1950 manufactured model 90 and after more than 25,000 rounds over the couple of years I've been shooting it, it still locks up as tight as the day it left the factory.
I'd like to hear from someone if they have worn out a marlin 90. As I stated, I've put 25,000 plus rounds through mine in a couple of years and it's still shows absolutely zero signs of wear in the action. There's no telling how many rounds were put through it in the 57 years before I bought it.
There's an error in the blue book regarding the separated barrels on the guns. It's actually the newer guns '49 to '59 that have the seperated barrels. The earlier guns have the Solid rib between the barrels.
The model 90 was made for Sears by Marlin with the pre war guns stamped Ranger and the Post war guns stamped JC Higgins. As part of the agreement, Marlin also sold guns through other channels with only the Marlin model 90 markings. After WWII the Sears guns also carried the Marlin stamp.
The metal finish on most of these old workhorses is very poor as the receiver is actually a malleable iron and will not take traditional bluing. They actually came from the factory with a Black oxide finish on the receiver. You will often find them with a very plum colored receiver which is what happens if you try to blue the malleable iron.
If you look inside you will see why they are so durable. They are powered by coil springs and instead of hammers and firing pins they have solid, inline strikers. A cool feature that most Model 90 owners are unaware of is that you can un-cock the gun by simply holding the triggers back as you close the action. (oops: I forgot to mention that you have to remove the automatic safety bar in order to do this)
The barrels have very long forcing cones and also very long parallel chokes. That explains why they are very mild kickers in spite of the relatively light weight and why they throw spectacular patterns. I love double triggers and extractors and the marlin extractor is a large single unit that is pushed out by the cam action of opening the barrel and is ultra reliable.
As far as prices. I paid around $300 for my 12, and $400 for my 20 and 16ga. I was patient and lucky on the small gauge guns though. $400 should buy an ultra clean 12 gauge version, and I'd expect it to last to hand down to your great great grand kids.
With regard to modern ammo, I would not hesitate with the exception of shooting steel loads.
Here's a photo of the guts of a model 90:
Weagle