It actually varied year to year, B-A. AFAIK the D720 started out as all gold (top of the line?) and at various times was silver with a gold gearbox, blue with a white gearbox
and orange with a white gearbox not to mention the OP's colour scheme, presumably somewhere in the middle. The only things I know are that the all gold was very early 1960s, followed by the silver/gold combi whilst the last all metal D720s in the 1970s (before they changed the shape of the tool slightly - new gearbox, new motor housing in plastic and angled rear of body cover also plastic - the DN720, etc) were orange and white.
The 2-speed gearboxes on all metal models almost all seem to have been 900/2400rpm - the hammer models, suffixed "H" (as in DNJ72H, DN720H) came in later on, 1970s, didn't they? Can't remember seeing an earlier all-metal one with hammer action. Other than the V-series premium drills in the mid-1970s did they ever exist? I do know that the hammer mechanism was generally turned off by rotating a black serrated or scalloped ring around the chuck shaft at the very front of the gearbox housing (at least on most pre-1980s hammer action models - there was also a gearbox in the late 1970s with a black slider on top of the gearbox).
As it happens before the introduced built-in hammer action there was a hammer accessory which fitted between the chuck and the gearbox which reduced the speed and gave an impact hammer action for masonry drilling. These accessories were offered for quite a few years after the hammer models came in. In fact somebody gave me one of these recently, salvaged from a relative's house clearance, and it still works (one of these is illustrated, below, on an all-gold D720). Not giving up my cordless SDS to go old school B&D quite yet, though
I like a lot of the old B&D all-metal drills - they have reasonable quality chucks in the main (the crimped horror in the photo below was a late cheapened one - note the differences in body cross section and gearbox shape) and seem very long-lived with a modicum of care. Made in the UK, mainly at Harmondsworth in Middlesex, too
Considering that all these T-handle B&D drills started out as descendants of the original U.50 drill made for only a few short years in the USA in the mid-1950s (and out of production before 1960) they were remarkably long lived both here and subsequently in Italy, France and Germany (where many originally British-designed B&D models ended up being manufactured in the 1980s)