Thanks for checking, Mica. It plays very well, so I’ll leave the nut, bridge, and tailpiece as is.
As for the birth date, the serial number has year 1975, but I would guess based on the body shape (soft upper horn) that most of the work was done in 1974 and it was finished in early 1975. 74-59 with a soft upper horn has a birth date In June 1974, 74-124 November 1974, and 75-174 with a newer looking upper horn shape was at the NAMM show in March 1975, so probably finished in January or February 1975. So my guess is that 75-AO13 probably falls between those with a finish date in early 1975. But I guess there could have been some overlap on either side of those range boundaries due to design experimentation. I checked for the birth date for 75-133, that has a soft upper horn too, but could not find reference to it, so wonder how it fits into the 59/174 range as well.