1965 AMPEG B18-N
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1965 B-18 characteristics: Chrome chassis shock-mounted to the lid, white silkscreened graphics, two channels with guitar and bass input jacks on channel 1, black stove type knobs, 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, one leather handle on top, two chrome handles on sides, 4 pin XLR speaker cable and jack, 4 chrome lid latches, chrome script logo, Blue Check vinyl covering, silver grille cloth, serial number sticker and stamp, 18 inch Cleveland speaker, baffling, matching dolly with wheels, literature.
The first serial number system are 6 digits in length with the following pattern: YMMNNN, where Y denotes the year, MM the month, and NNN the # unit produced that month. The # unit, however, may not have started with 001. Ampeg may very well have used 100 or 101 as the starting point during slow production periods. Nevertheless, for dating purposes, the serial number provides adequate information during this period. For example, an amp with serial number 406123 was made in 1964 (4), during June (06) and was probably the 123rd amp made that month (123).
The second serial number system was implemented in January 1965 and used until the end of 1969. This system overlapped with the previous serialization scheme for a period of about 6 months. These are 5 or 6 digit numbers which appear to have been applied sequentially, but are not date encoded. 1965 serial numbers ranged from 000001 to 020000. For more precise dating cross reference the serial number with the amplifier's transformer, potentiometer, capacitor, speaker codes and vinyl covering.
However, caution is needed for dating amps from 1965, as the serial numbers from this year were already used in 1960. A serial number 009054 could be from September 1960 or it could be from the second serial number system implemented in 1965 (above). The key is the model and the cosmetics. For instance, the B-18 wasn't introduced until 1963. And an Ampeg from 1960 would be covered in navy random flair vinyl whereas an amp from 1965 would be covered in blue check vinyl. Another check for a 1960 versus a 1965 or later serial number (i.e. numbers beginning with 0) is that the second and third digits of the number denote the month in the first serial number system. Therefore, a serial number where these two digits are greater than 12 must be from the second serial number system (1965-69).