The original Colt slide that was on my M1911 has no peening damage. The Ithaca GI slide now on it came from a gun show back in the 1980s, and it was a brand new and complete upper, consisting of a slide, barrel, spring, and barrel bushing. I think I paid $75 for the whole package. I later applied a black spray and bake Teflon coating to the slide to match the blued frame better. The M1911 looks good, works fine, and I have no regrets I refinished it. I did all of the refinishing myself, so it didn’t cost me much.
One reason I bought the Ithaca upper was that slides of the WWI era were not heat treated, as related above, and are prone to damage. Later ones were heat treated.