1966 AMPEG B15-N
By 1966 the tilt back rod was gone. Gibson continued to transition serial numbers from stickers to being stamped onto the back left hand side of chrome chassis. The chassis was shock-mounted onto the lid. During the year a patent number began to be silkscreened on the back chassis below the fuse. During the year the top handle began to change from leather to vinyl.
Other 1966 Portaflex characteristics: White silkscreened graphics, two channels with guitar and bass input jacks on channel 1, black stove type knobs, CTS potentiometers, three metal switches, two large black transformers, black tube cage protecting the tubes and capacitors, light up plexiglass logo (which could be personalized for an additional charge of 50 cents), fuse, two prong power cord, schematic, 4 pin XLR speaker cable and jack, 4 chrome lid latches, chrome script logo, Blue Check vinyl covering, silver grille cloth, 15 inch speaker, matching dolly with wheels.
The second serial number system was implemented in January 1965 and used until the end of 1969. These are 6-digit numbers which appear to have been applied sequentially, but are not date encoded. 1966 serial numbers ranged from 020000 to 049000. For more precise dating cross reference the serial number with the amplifier's transformer, potentiometer, capacitor, speaker codes and covering.