For my money, the Lyman 48 in about all its forms, the greatest tech and most svelte of the several fully adjustable receiver sights of its class! Your model shown appears the second of three models. The fist with a 150 denominated slide. Yours, 125 and more practical for most purposes. Your sub-style earlier version with small adujstment knobs. Itself, likely pre WWII and 'renesting' on your postwar build. The one significant downside of this great sight, IF ever removed permanently, leaving one very large inletting canyon. The third model, considerably smaller slide but in most cases, installed without need to inlet. The net, net here as I see it, a plus due to the great Lyman nesting there!
Below, reference pix, second model Lyman 48, as original govt installed equipped on genuine US Springfield, "NRA Sporter", c. 1924.
Congrats on that nice looking rifle there!
My take.
John