AMO is meaningless for a '52 Bear; the standards didn't exist back then.
You need a string that will brace the bow at the recommended height, which for the early 50's bows is the good ol' fistmele, or about 6-1/2".
AMO standards state that the AMO bow length is 3" longer than the string needed to brace the bow properly - not 4". Any bow that needs a string 4" shorter than it's marked isn't marked to AMO standards. Only aout half of the bows I've made strings for over the last 5 years were actually marked by the proper AMO standard.