The Ol' Mongoose was a late bloomer,in the same way as Jersey Joe Walcott was. When they were young they both had to take fights for chump change,because of economic circumstances. When would you say Archie was at his very best ?
Archie Moore didn't start to hit his stride until after his stomach ulcers were corrected with surgery in 1941. But it still took him many years to recover and put healthy weight on. He learned alot from the Burley, Bivins, and Charles losses, and got better from experience in general. His most successful run 48-55. He picked up most of his signature wins in this period while appearing his most domintant in the ring. If that isn't his peak, I would have a hard time picking another timeframe. Perhaps you could even extend this run into 1960 to include the Durelle rematch.
Earliest footage I've seen available on youtube is 51...I think. His impressive first round Ko of the 25+ heavier Davidson and the final Bivins fight.
The best and most exciting performance I've seen available on youtube is the 53 Valdez fight, the last Johnson fight from 54 is another great one with Moore coming from behind to win...an usual spot for him. Pretty important fight too, coming off wins over both top heavies Charles and Valdez, Harold Johnson was in a position to challenge Marciano if he got past Moore.
Yarosz, Zivic Win Easily . Pittsburgh Press - Google News Archive - Apr 21, 1939 LOUIS, April 21 Teddy Yarosz. Pittsburgh middleweight outboxed Archie Moore, St . Louis Negro, last night to win a 10-round decision at the Municipal ... http://news.google.com/newspapers?i...AAAIBAJ&pg=5029,2363495&dq=yarosz+moore&hl=en