I am wondering if S&W produced a pre-model 10 in alloy frame with steel cylinder and barrel. The Model 12 was the alloy model of the Model 10. Barrel has "Airweight" stamped on it

Yes. The Airweight version of the .38 M&P post-war revolver was introduced in 1952. Originally, it had an alloy cylinder as well as an alloy frame. This turned out to be a bad idea and the cylinder was replaced with a steel one.
The early examples also had what was called a "bug" screw at the top of the sideplate to secure the upper sideplate screw, due to the problem of only having a few threads engaging the aluminum allow frame.
One other detail - the frame on these guns is of slightly smaller dimensions than a standard K frame revolver.
What is the serial number on your example?
Regards,
JP

__________________
Jack
SWCA #2475, SWHF #318

And please pardon my manners.
I forgot to say, Welcome to the forum. I think you will find there is a wealth of information and great enjoyment among the members who participate here.
JP

__________________
Jack
SWCA #2475, SWHF #318

have a newly acquired pre model 10. pretty good shape, slight rust but no slop or pitting. not the wood handle but is a snub nose. trying to put a rough age on it. serial is 273xxx. any ideas group?