Dan,
Look on the back(transom)of each hull where the rudders attach:
The format is as follows: CCMX0000X000
CCM = Coast Cat Manufacture (Corporate Name)
X = Model letter (typical... 18s are C, 16s vary, Wave X, H20 P etc)
0000 = serial number
X = Letter / Month of Mfg. (A is January, B is February etc. I is not used I don't think)
000 = year of mfg and year model (797 is '97 mfg. 97 model / 697 would be a boat built in year '96 but is a 97 model. Model year starts in July.
This article is taken from On The Wire - the eZine for Hobie Sailors
Great beginning catamaran for a lot reasons listed in this thread.
I had my first when I was 12 and my second when I was 35.