Additional picture

Not sure if someone was attempting to make a takedown out of a solid frame or not. Don't think there are enough threads left in that receiver to hold a barrel even for show.

Look at the inside the tangs and on the front of the action to see if there are marks that indicate its past. There may be inspectors initials or other identifying marks. For example, MNS or MVNS probably means that the material is Midvale Nickel Steel. Campbell's books have a lot of the details on marks. I'm almost certain that Action E was made of an experimental type of steel.

Dr Tom

I am reasonably sure the action is one of the patterns use as gauges at the Winchester factory. According to the Campbell books there were 20 drawers of model parts. It looks like someone has done a bit of grinding on the action and I would doubt if the tang is original to the action. There was a  mate to this action with the same notch in the barrel shank for sale with in the last year which was in much better condition. I do not remember who had it but it was also listed as pattern.

These parts were used a gauges to be sure tolerances were kept and parts would interchange. If you look at page 197 of Volume one of the Campbell book you will see what the drawers looked like. Most of the parts were marked or had tags identifying what they were.

Cheers,
Laurie

JWL, 

Do you have a picture of a front view of the action looking straight at the firing pin hole in the breech block? 

My guess is the mark is MVS which is for Open Hearth Soft steel from Midvale Steel Co. It could also be  MNS which is .45 Carbon Steel. For what ever reason Winchester used the first letter of the company followed by NS for the 3 companies that are listed in the Campbell Volume I supplying .45 Carbon steel. 

MNN is the mark for Midvale Nickel Steel. 

Cheers,
Laurie