Although the most important questions are already answered, I might drop in my 2 cents:

• The central chrono second hand is wrong (fyi, I just saw 3647 hands offered on Chronotrader – I assume that the second hands are identical to the 2447)

• No worries about the missing reference number, this was only introduced a few years later with the second execution of the 2447

• As for the "black rings" around the counters: I think they are not painted, but it is just that the silver color has deteriorated around the sharp edge of the step. I have seen the same effect on an early 3647. You can see from the "freckles" on the dial that the colour is prone to deterioration.

• At first sight I was surprised to see a silver dial on such an early serial number, but looking at the OTD master reference table, it seems just fine.

• I agree with Mark assume the signed crown was added during a service, imho it should be unsigned for this serial number. But being an original and genuine Heuer service part, there is nothing wrong with it.

Regards,
Robert

IG: @heuer_carrera
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: Yes, the second register hand is a replacement; the crown probably
: is too, it wouldn't have been signed back then. The poly back is
: fine and no model number being engraved is entirely correct,
: that was a later addition.

: Looks an honest example to me, with a few changes made at
: servicing, probably with what parts the watchmaker had at hand.