number 1 is original as the bowl is angled and threaded ,number two is the spaco/later types where the retaining screws are upwards as opposed to downwards as per the first .
i stand to be corrected though .some bowls are angled and screwed up tho
In fact the screws for No 2 are from the top down and the No 2 version is also on my SH1/20.
Version No 1 was fitted to the SH22/2 when I acquired it (atomiser and slide for GP150). I don't suppose it makes much if any difference to the operation of the carb and I was just curious as I didn't recall having seen the No 1 version before.