Significantly revised at 2024-01-10 with the discovery of new serial numbers which clarify several points that were speculative earlier.

A list of known ELEX K1, K2, K3, K4 serial numbers (including rebranded models). These seem to come as 2-part numbers; it’s not certain what the parts are, but it seems likely to be batch and serial. (It isn’t week and serial, as it’s continuous across at least four years of production, 1976–1979.)

(For details of the instruments and revisions see here. The rn for revision+number is my addition, not part of the original model numbers.)

The numbering system found here may have been introduced with the K1r2, but no K1r1 number is yet known.

Revision 1 K4s had an external power supply and volume pedal, like some older electronic organs. The serial number / rating plates were on this unit rather than the keyboard itself. These are rarely photographed and are sometimes missing. There appears to have been a revision 2 with some differences in the power/pedal connection. K4r3s have a different case but no internal photography has been found.

So long as we regard the parts as separate (or assume a zero-padded second part), the known numbers seem to be in a continuous sequence across the revisions, between models, and across all brands. The same system seems to have been used for at least some other ELEX instruments at the time ^[1] but it is not clear whether the other models used the same actual sequence. Unless this point can be clarified (by finding a number collision between models) it will not be possible to use the numbers to estimate production volumes. (The later EK 2 and EK61 had four-digit serial numbers, so are not part of this sequence.)

(With the uncertain exception of 21 14) the serial numbers found in batches 20–31 have a prefixed slash. ^[2] All numbers known in these batches are two-digit, so it is not yet known how one- or three-digit numbers are treated, if there are any.

With the discovery of another new K2 serial number it has become apparent that the revision sequence I had used earlier is wrong; the earlier ‘revision 1’ type is later than the ‘revision 2’ type, so I’m reversing that numbering.

Most of the examples found are Hohner-branded. Other brands are noted in the table. Anecdotally, the String-Orchestras (both black/silver and wooden) are often said to have been sold by Farfisa.

From which, so far, conclusions are:

• The K2 type with the pedalboard connector and trimmer on the underside is the original version. This is now regarded as revision 1 here and elsewhere in this site. ^[3]
• All three known K2 branding types, ELEX, Hohner, and String-Orchestra, were used for r1, r2, and r3. ^[4] (One K2r3 with Excelsior branding is known, from the time after ELEX ceased to operate as an independent brand.)
• The K4 (r3) blacktop was probably introduced before the K1 (r6) blacktop.
• (Tentatively so far) it seems likely that the K2 wooden String Orchestras did not have stand attachment plates, but all others did.

Appendix: Power ratings

The power ratings given on the K1 and K2 models vary for unclear reasons.

K2r1s all seem to be 16W. K2r2 plates I’ve seen photographed are mostly 25W but some are 16W. At the time of writing I haven’t seen any interior shots of an r2.

K2r3s may be rated either 16W or 10W but I have concluded that on a K2r3 I’ve been working on, the power rating is simply wrong, as if a 10W rated plate was put on the back just because they’d run out of 25W ones. Its actual power consumption seems to be 22–23W. This implies that none of the power ratings for this model can be trusted, and cannot be used to establish anything about the sequence or circuitry changes.

The only K3 plate I’ve seen with an interpretable power rating was 18W. All K4s with visible plates are 14W.

Appendix: Diagram Dates

I’ve found the following dates on service manuals and schematics for these models, and what I think are diagram numbers rather than model numbers:

These dates were all found on front pages or covers for the documents. Unlike some other manufacturers Excelsior seem not to have dated the actual diagrams, and never seem to have given revision numbers or dates. After 1978 they seem to have stopped giving the dates on the covers too.

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