Heating unit age

Hot water heating unit age please
M# 24VA03
Ser# FC215474331843

Aquatherm is a difficult one.

My best educated guess is that I think that serial number is from March 1977. I also have some conflicting information that indicates it could be 1967 or 1974. So what makes most sense to you in considering other aspects of the property?

The house was built in 2001 so I don’t think it’s either. The compressor outside has a manufacture year 2001

I’m stumped on that one, then.