Hi Doug-

I may be able to help some here, if you’ll excuse the fact that some of the sights I’ll show are not attached to M54s.  The M54 differed somewhat from the early M70 as far as how the factory handled barrel mounted rear sights on rifles equipped with a factory receiver sight.  Bert, please feel free to correct me here…

First is the Lyman 48W (not WJS) receiver sight.  These were generally “long slide” sights that required the “T” shaped stock inletting.  The 48WJS (that often had a shorter “75 point” slide not requiring inletting for the extended elevation screw) was not introduced until about 1936.  This is a 48W on a M54 1st standard rifle:

Second, is that when equipped with a receiver sight the M54 usually came with a Lyman 6W sight in the barrel dovetail.  The Lyman 6W had two folding leaves that allowed it to be folded flat.  Sorry the sight in the photo is not in the center of the photo and that the rifle is a straight taper 375 MAGNUM M70. But it’s good enough to show the sight:

Unlike the M54, most (but not all) early M70s used a Lyman 12S slot blank instead of the Lyman 6W:

But the cataloged sight on the M54 with receiver sight was a 6W as above.  Maybe later M54 “NRA standard rifles” used the blank, but the 1st standard rifles most likely had a folding leaf 6W.  Also, the blanks provided by Lyman to Winchester were only marked underneath, not where they can be seen.  If the blank is stamped “LYMAN” (or any other maker) where it can be seen, then it’s probably a later addition.    

FINALLY… When the M54 was NOT equipped with a receiver sight, it used the Lyman 66W sight, which has one fixed and one folding leaf:

Sounds like a nice rifle.  I admire your interest in making sure the gun is correct.  I not too long ago acquired a decent 1927 M54 1st standard rifle in .30 GOV’T’06 off Dave Morris b/c that was the year my Dad was born.  Top pic above.  Gave it to my Brother…

Hope this helps…

Lou