Ahh lets have a "Ripper serial number" debate again, must have been 3 months since the last one
The bird is right telling you it's on the outside of the right drop. they start from PK2 (which are the most desirable of the numbers) pre serial more so.
Use this as a guide.
78 (JU-6, BD-III's). No SN's.
79 (PK, DB-IVs'). No SN till later in the year, started with 2xxxx.
80 3x
81 4x
82 5x
83 6x
84 7x
85 SE in house now.