It's my opinion of serial No. from my archives.
Following digit stamps are confused.
No.0 : c,o(alphabet), 6,8,9(double stamped)
No.3 : 8
No.5 : 6
Serial No. with extra letter. (following are in my archives)
A--- : 1974 (Dela'217s A013), 1975(unusual omega A051)
AC--- : 1975(AC025, AC033), 1976(AC070, JimmyJ's AC418)
AE--- : 1976(AE013 t0 016 for YAMAHA, AE069, AE082, AE40?)
o-- : 1974(o13 as Smithsonian bass, o18)
AC418 and AE40? are added AE,AC on regular serial No.
I think these were started to build as regular, then added stamp when exported it.
Other instruments were prepared for specific.
In this case, I confused the picture.
Frettless on left side is LSB #O86 and Fretted old style is #025-75, all right ?
If so, older bass(right side) is 75 o25 that I think.
Very few 75's standard body had round upper horn.(I said 74 style in my last post)
No possibility as 72'025, AC025(double neck) and AE025(1976).
Now, #086,
Body and PUs are late 1975 style.
Single trussrod featured before 1977(serial No. arround 650).
Regular serial No.86 is 1974.
Because, 1976 AC or AE086, or 1975 o86 are compatible for this case.
I wish Mica will suggest about this.
Sorry for your confusion due to my representation.
I wrote with dictionaly but difficult.
Eiji