well, i shoulda checked the website first... lol... for future reference, hartke amps can be dated as follows:
Support | Samson Technologies
The number before the letter indicates year of production. 5500 - 5H9C00012 = 2009 PRODUCTION. (5H = Model 5500 - 9 year - C = 3rd month (A=January, B=February, etc.)
Looks like mine's a 2000. I'm going to rule out a 2010 because it's wayyyy to beat up to only be a year old.