A 4" M15 was my very first duty gun, issued to me in spring of 1983 in Shenandoah NP. The district ranger opened a ratty old locker inside the caged armory area which containied a couple of heavy barrel M10's and the loan M15. "Which one would you like?" No hesitation, ""I'll take that one."
I removed the walnut sevice grips and added a pair of Pachmeyer large square butts, legal modification. Surprisingly the adujustable sights were bang on with the at the time duty load of 110 gr JHP +P+. With years of service behind it, the action was smooth and slick, but lockup was still tight. Finish was still surprisingly good, it had been well cared for. As far as I could tell, it was the only M15 in the park, I never saw anybody else carrying one in any of the three districts.
I never fully appreciated that revolver at the time .....and would jump at the chance to buy it's equal at a decent price.