Here is some info I put together for another forum, it will only date your gun within a 13 year span......
The model 3 first appeared in No 66, price list dated Jan 1932
The model 4 first appears in No 67 (I do not have a price list but I assume 1933)
.....There is no mention of stock finish for the 3 or 4 - but for the 23-AA in these catalogs it states "hand rubbed varnish". In No 70 (march 1936) the 23-AA is listed with an "oil finish" . (in No 67 the 23-D descrirtion says "Oil finish $5.00 extra).
---->In catalog No 70 (March 1936) the No 4 is shown with a checkered stock - not mentioned in the descrition
Catalog No 74 is the first to actually list checkering and oil finish in the descrition for the model 4 (the Model 3 does not show nor mention checkering)
The 1948 catalog (first catalog to drop numbers and just use year) the Model 4 still is describes as having checkered stock and an oil finish.
---->1949 checkering dropped but oil finish still in description
The catalogs do not list the alpha characters on these models in the catalogs so there is no way using catalogs to tell when the 4 was changed to the 4B etc.
1954 is the last listing and it's still just listed a Model 4, in 1955 the stock was changed to a monte carlo style with a larger fore arm and it then became the Model 4 Deluxe - which was the only version cataloged other than the 4-S Deluxe which just had special sights (peep etc).
There were two different notch heights for that rear sight, I had thought that the taller was to be used with the hooded post front sight. My 7-S has the taller one and the hooded front but I see Mad_Dog's has the lower version. I have other guns using the lower version of this rear but they have standard post front sights. These sight will also be found marked "PATENT PENDING" which might help the date - patent granted June 15, 1937.
Sights that came on a -S version, the sighting disk with 3 apertures was only used for the first couple of years - later guns were shipped with 2 different disks.