http://en.wikipedia.org/wiki/Haro_Bikes
Haro Designs
The company was founded in 1978 by
Bob Haro. Haro started out producing numberplates for
BMX bikes in his bedroom. Demand for these stylish plates quickly outgrew his one man capacity. Haro Designs, the first name of the company, was formed in 1980 with headquarters in
Torrance, California.
I'd start with the SN, see if there is any obvious code to it ?