Probably worth noting that the smiths number on the dial is not a 100% guarantee of whats actually inside, or for that matter outside.
For example, for a while, until computer printing of dials on a one off basis became possible the speedos restored or recalibrated (to a different spec) in NZ either retained the original (now incorrect) dial, but only if it was good enough to be reused, or they had a new dial fitted with no number, or if that didn’t suit the owner potentially it was fitted with a new dial with a wrong number.
I’m glad I have the two chronos I need for my A10 and B31, but if I didn’t I would get any old chronometric and give that as part payment for a restored one (from a specialist restorer) of the correct spec.
Local situations will vary but parts for some trip reset arrangements were once (possibly still are) in short supply, so it would be best to buy one with the correct trip eg either side or bottom, to use as part payment.