I found this somewhere but I think there was something about the letter in your serial # ( H, M, S, Huffy, Murry, Sears):
Huffy Serial Numbers
Determining a Huffy's age requires two steps:
The last digit of the year of manufacture can be determined by the first digit of the serial number.
Then you have to look for other characteristics to determine the decade of manufacture.
Example:
Your serial number starts with "5"
Your cycle has 26 x 1.75 tires
Your cycle has a built in tank
This would be a cycle manufactured in 1965
Can't remember where I kept my Huffy stuff (62 in my avatar box to the left) in my computer but I hope this helps.
GL