Lyman 48 selection is further complicated by the myriad of styles and dimensions that evolved over time. The earliest examples had the 'full block' base with the elevation screw's bottom end being captive against the inside of the long slide and with relatively small adjusting knobs and 1/2-minute clicks. Later the sight was offered with larger target-style knobs and 1/3-minute clicks as well, with a shorter slide as described in the post above...
This sight features the full block base and the captive elevation screw.
Either way, it's the front sight I'm interested in finding out about the issue date - but it's all just curiosity around guessing the time that this rifle was made.
Could be any time after the sights were made.
The only marks from the maker that I've found so far are two punch marks and the number 50 inside the toe of the checkered steel buttplate.
Always something to ponder.