For Yamano Gakki Epiphone Japan semi acoustic models from 1987 to approximately 1997, the serial numbers are in a YCPPP format. They were made by Terada and usually have an Orange Epiphone label.
The Aria Epiphone Japan models that were made by Matsumoku from the early 1970s and ending before 1987 do not have a reliable serial numbering system but can be approximately dated using their Epiphone label colours.