You do indeed have a Springfield Mark 1. As you probably already know, most of those were stripped down and their special triggers, sears, cut off switches and spindles were replaced with regular 1903 parts. The original stocks also had a notched area below the ejection cut out on the left side. Those stocks were reused and dispersed to be used as replacements. There were a number and still are a number of Mark 1's that escaped the strip down, some were sent as is to be used in legion posts for burial detail etc. Later sold through various government programs.
Once returned to service, they were subject to rebuild just like any 1903. Yours has gone through a rebuild. The barrel and rear sight sleeve are 1942, the gun made around the end of Dec. 1919, maybe Jan 1920.
The bolt appears to be a Smith Corona 1903A3, possibly a Rem of the same model. The stock is a Springfield C stock and although very unlikely it was put on at rebuild, anything is possible. More likely it was replaced by a civilian as the handguard is not quite right for an original. The cut off switch notch on the left side has been hogged out, again, not what you typically see from the military. The front sling swivel is on backwards, the U stamped on the side should face the front of the rifle and the screw head on the right side.
As to value, there are a lot of things that add and subtract. The stock has value but is somewhat degraded by the hack job around the cut off and is not an original Mark 1 stock, still....
The bolt is not original nor are any of the parts such as the cut off switch and spindle. I can't see trigger or sear but assume they are not original. The bottom metal, trigger guard is milled as it should be but details may or may not help.
The barrel, condition is everything on a rifle like this, it would be a shooter and needs to be in good condition. Head space needs to check ok too.
Bottom line, it's a rebuilt and somewhat messed with Mark 1 and it's basic value would be as a shooter example. Kind of a nice one with the C stock I might add. Assuming everything checks ok, then $400 to $500.