If your knife is marked Schrade Walden it is not from 1920 it had to be made between 1946-1956 approx which was the time this marking was used on automatics. If your knife is marked Schrade Cut Co then it could have been made between 1903 and 1946. The pat Numbers and dates would help somewhat to discern approx when. These knives were made in three sizes 2,7/8" 3,3/8" and 3,3/4" . Yours sounds like the 3,3/4" since you state the pearl is in one piece It would seem that it has no bolsters ( this size was made with small tip, full bolsters, and no bolsters ). In a Schrade Walden 46-56 approx these in this very large size in pearl were even more rare than the Schrade Cut earlier versions. )..
So first the bad news usually these in pearl have been rehandled especially under Schrade Walden. These were usually in celluloid which often would decompose the result was that if the knife was in good condition it would be rehandled either in jigged bone or pearl to make it look original. Cell while still available is usually pretty easy to determine if new or original by the pattern. So since this size pattern knife is quite sought after, it is easier to use jigged bone or pearl. The old style jigging on bone is difficult to copy so if this is used it to can be a give away. However the one material that it is almost impossible to tell from original is pearl. Some people will tell you that old original pearl can be determined by flaking ect. If so more power to them in most cases it all looks the same ( at least to me ) them oysters have not changed there production methods for some time. The model under Schrade cut is a 7504. (NOTE this then has a letter to determine the handle material however this is not on the knife only the catalogue ) I have now searched in a sea of paper for an hour and cannot fine the catalogue which shows the model under Schrade Walden . However I believe they did make the 3,3/4" under that tang. and usually they use the first three digits making it a 750??? Very few original pearl were made fewer in Schrade Walden and the least in this size.
All that being said the Good news, is that you still have a very sought after piece. In really good shape 350 and up in that size maybe ( if the right people want it ) 550+. That is a retail price and I have not seen the knife so it is pretty much a guess until I know condition however usually these are in great shape because it would make no sense to rehandle a beat partser to put pearl on it. ( which is another hint that it was rehandled) So it is only a guess but, I bet yours is in nice condition.
All that being said it could be original but really it dosent matter price wise. Let me know what else you might need. I have to look for that damn catalogue. LT PS I believe you can fire both blades at the same time by pressing the buttons at the same time, but why would you want to????
