One number, several machines
Hammond issued serial numbers along production lines, not across the company. The consoles run as one continuous line — Model A, then BC, BV/CV, B-2/C-2 and finally B-3/C-3 — which means a B-3 and a C-3 of the same year sit in the same numeric space, and you cannot split them apart. Spinets (M, M-2, M-3, M-100, L-100, S, T), consoles D, E, G, RT-series, A-100, H-100, X-66 and every tone cabinet have separate runs.
The practical consequence: the same number means different years in different rows. The number 28000 in the console line is a BV/CV of roughly 1949 — it is not a 1955 B-3. The first 1955 B-3 block starts at 56014. Any page that decoded your number without knowing your model was reading the wrong row.
Step one: find the plate
- On organs from the 1970s onward the model and serial sit on a plate under the lower keyboard, left or right.
- On older consoles the plate is elsewhere on the cabinet — rear panel, upper areas.
- Deceptive lookalikes: “Hammond” also appears on Hammond Manufacturing (industrial enclosures) and on Hammond typewriters. Check that the plate actually belongs to an organ.
Step two: pick the exact model group
Use the model stamped on the plate, not “it looks like a B-3”. Choose the matching group in our Hammond decoder — consoles, spinets and tone cabinets each have their own tables. If your organ is a spinet, don’t feed its number to a console table; the rows are unrelated.
Step three: read the block, not the digit
The published table is built from owner registrations that submitters verified against physical date codes. Where a year has enough reports, it becomes a block: a serial range that “belongs” to a year. Blocks get you within a year or two — the list itself says so — and that is why every answer from us carries a confidence level instead of a fake exact date.
The 1969–1973 letter era
Organs built from 1969 to mid-1973 carry a leading letter on the plate, and the letter — not the digits — sets the year: A=1969, B=1970, C=1971, D=1972, E=1973. These organs were removed from the digit registry, which is why digit-only charts show a gap in that window. If your number starts with a single letter A–E, read the letter.
When the table can’t help: read the components
For any Hammond, the physical machine can outvote the table:
- The AO-28 preamp transformer is silver before 1963 and black from 1963 — black transformers often carry a 4-digit date code on the bell.
- EIA date codes on transformers, potentiometers and speakers give year and week (three-digit maker code, then year, then week).
- Capacitors and motors carry their own stamps; the oldest original component sets the floor for the build date.
Cross-check with model production years
- B-3 / C-3: 1955–1974 (the Blue Book says “1955”, Wikipedia “1954–1974” — the usual one-year argument).
- A-100: 1959–1965. M-3: 1955–1964. L-100: 1961–1972. M-100: 1961–1968.
- T-100: 1968–1975. RT-3: 1955–1973. D-100: 1963–1969. X-66: 1967–1973.
If a decoder answer contradicts the model’s production window, distrust the number — a re-stamped plate or a swapped lid happens more often than one would hope.