The aquired RVI tachometer did not work, so a repair was necessary. The circuit board was in a fairly bad shape, but fortunately the board from the aquired RVP meter could be swapped. Apparently, Smiths used the same circuit boards for several models. The two transistors were unidentifiable (not the standard GETs), so they were exchanged with two AC 128 (NTE158 is difficult to source in Europe). The major capacitors and a few resistors were also changed and, voila, a working unit.
A note on bezels. The old, nice full-V bezels are no longer available for 3″ instruments, so care must be taken to save the old one which is not always possible. Apparently, these bezels are avaiable for 2″ and 4″ instruments so maybe there is just so much more demand for 3″. One can only hope that someone starts to produce them again, and this time slotted so assembly is easy.