1.) S&W Model 36, S/N J8870XX
2.) S&W M&P 1905 3rd Change, S/N 1955XX
J8870XX = 1981.
On the 3rd change M&P, serial numbers ran from 146900 in 1909 to 241703 in 1915.
You're M&P is scarce target version which doubles it's value.
I do not know what bluing process S&W used.
S&W .38 CTG - No prefix serial # 784xxx
Serial number dates it to ~1940.
38 S&W ammo is still available.
I would not refinish it but I would get it checked out to make sure it's safe to shoot.