Well i can tell you the owner made some effort to buy a look-alike strap ( nice touch )
i'm not convinced the bracelet is for this watch - even if it turns out to be Heuer signed.
The seller is correct, there aren't serial numbers or at least there aren't any visible on my example ( maybe something to do with the different metal used to produce the case or indeed the following chrome/PVD process ) - this leads to a further question - do the famous black manual Monaco's have a serial number?
The case back has a model number stamped into it for sure. My Cal.15 has 150.501 clearly stamped.
Hope this helps -

- Darren

: BTW Darren - owner has said the lthr strap is aftermarket and the
: PVD strap came with the watch 3 years ago, he assumed original
: but im awaiting if it is signed (cant see signage in pic) but he
: confirms it appears to match case PVD'ing (is that a word?!)

: Should the lugs or caseback have a serial no, as he confirms they
: do not on this one?