Look on the main board - does it have an '020, '030, or '040? The main board in this case is the one with the internal hpib interface, a 9-pin serial interface, a HIL interface, possibly a LAN interface (I don't recall the 320 having a built-in LAN), could possible have a speaker jack also (for the HIL beeper). If you don't see a CPU/FPU on that board, then check one of the ``memory'' boards, which will be full-size DIO-II card if this is the case...If I remember correctly, the 360's CPU is not on the human interface board, but rather a CPU/memory board that connected via a ``bridge'' connector to another memory board. If you can find the CPU, look for it's oscillator, and half the frequency. This should be your clock speed. :
310: 16MHz 68010 (runs hp-ux 5 and PAM - bleah...)
320: 16MHz 68020 (ROMS prolly say `Rev. B')
340: 16MHz 68030
350: ??MHz 68020 (I think 25, but I'm not sure...)
360: 25MHz 68030 (I've always seen these in ``single high'' cases)
370: 33MHz 68030 (I've always seen these in ``double high'' cases)
375: 50MHz 68030 (seen these in double and single cases - they have an L-shaped daughterboard with an '030 and '882 that sits in an '040 socket...)
345: 50MHz 68030 (these are like 375's with different cases - thin like the old 700X Xterminal cases, longer than other hp300's, too...say 345 on the front. Only one ``spare'' DIO-II slot for a video board...)
380: 25MHz 68040 (these are 375's with newer roms and an '040 in the socket instead of the daughterboard)
The memory in the 345, 375, and 380 is sort of simm-looking, but has lots of pins (I've never counted them...) in the sockets, and corresponding connectors on the memory-boards...They're about the same size as 36-bit simms for EISA PCs... If it has multiple (>2) memory cards it is a 320. If it just has a single card (well actually two cards bolted together) it is a 350. As far as I can tell, the 360 and the 370 are very similar - they use the same type of memory boards (or, at least, they look the same), etc. Not seen a 340, but I've read about them...I think the roms on these things said `Rev. C'... If it were a 400-series machine, it'd say so on the front...along with `Apollo' - go figure...