Alan,

If the rifle is in the original configuration, excellent bore, has no cracks in the stock, has clean original checkering, and 95% blue then I would expect it to bring well over $2000.

If the rifle has been altered, has a cracked but repaired stock, little blue but no rust, and is in serviceable condition with a good bore, then it should still bring $500 to $800 as a shooter.

Of course that leaves a lot of in between ground for all those rifles in between. I remember seeing one that sold for over $2800 and a couple of rusty parts rifles go for around $400. Besides condition, things that add to desirability are caliber, sights, and model. Caliber - rifles in .250 generally bring more than rifles in .300. Sights - the bolt peep sights are desirable. Collectors (not me) are knowledgeable about the various types of rear sights that were used and some are more desirable than others. I just don't know which ones. Model - the model 20 rifles (1920-1926) are more petite and generally more sought after than the model 1920 rifles (1926 and later).

The middle rifle in the above photos has British proof marks. Why and when are a mystery. Odd features like that may increase desirability to some people and decrease desirability to other people. In the end, something is only worth what someone is willing to pay for it.