The serial numbering system had changed in recent years.
Standard Collection:
1 (identifier) YY (year) XXXX (numerical ID)
Custom Shop:
HC1 (identifier) YY (year) XXXX (numerical ID)
For example, a serial number of 1219876 or HC1214567 would mean that your guitar was built in 2021.
The old scheme used letters to designate the year and day of manufacture.
HANDWRITTEN SERIAL NUMBERS
These Heritage guitars have a serial number that begins with a letter (e.g. D12345). Numbers following the letter is the # of day to Dec 31. Jan 1 would be 365, Dec 1 would be 030. The system was discontinued.
Letter on Serial #: B Year Built: 1985
D - 1987
AA - 2010
AP - 2025
So a Serial # of Q23501 should be the Tue, May 9, 2000, 130th day of 2000, and the first number assigned that day. I don't know if Leap Years messed up the numbering system. It might have been Mon, May 8 since there were 366 days in year 2000