1970s? More like 1960s or earlier because Wolf replaced all the metal bodied heavy drills with the new Sapphire range in the very early 1970s at about the time they went to "plastic" bodies.
The WD5c/WD6c drills were certainly in the mid-1960s Parry's catalogue, though. The WD5c is listed as 5/8in chuck, 595 watts (input), 560 rpm free running speed,, 350 rpm full load speed.
Wolf were taken over by Kango's parent firm, Dobson Park Industries, in 1981 and the two were merged to form Kango-Wolf Power Tools in December of that year, at which point almost all new power tool development for the Wolf brand, other than an SDS drill, seems to have more or less stopped. Wolf had already been buying in planers and belt sanders from Makita from the late 1960s as well as having abandoned manufacture of the Sapphire jigsaw in the mid to late 1970s in favour of a bought in model from Perles. IN the 1980s a new small saw from Perles was added to the line up (as a Kango) with belt sanders, jigsaw and planers coming from Holz-Her from about the time Makita commenced manufacturing in the UK at Telford in 1988. It is notable that even in the 1970s Wolf had to buy in Makita mini grinders for a while to cover production delays getting their 4-1/2in Wolf Grinderette into production
The merged firm, based initially at two sites in London (Wolf at Hanger Lane, North London whilst Kangi were at Morden in Surrey) eventually moved to a new site in Peterborough in the late 1980s having been progressively rebranded (and reliveried) "Wolf Power", "Wolf from Kango" then just "Kango" (the firm was officially renamed just "Kango" in March 1988). But the lightweight stuff they were selling by 1992 was pretty much what they were selling in 1982, only Kango receiving any development effort, and there were big gaps in the line up, like planers, jig saws and belt sanders which were filled from 1988 onwards by buying in from Holz-Her in Germany.
The electric power tools division of Dobson Park was sold to Atlas-Copco in May 1993. Dobson Park, a deep mining equipment manufacturer, retained the Kango pneumatic drill and drill bit operation until their take-over in 2017, since which time some Kango products have been made in South Africa and SDS bits, etc made in Germany (name licensing?). After buying Kango A-C fairly soon merged it with the far larger AEG power tool division it had acquired, almost immediately replacing Wolf designed drills with rebranded AEG items, before moving all manufacturing to Winnenden in Germany, at which point all remaining ex-Wolf products disappeared, the last Wolf-designed saws and drills being made in 1984 as far as I can ascertain from serial numbers.
The Kango name was retained and these days is found on some Milwaukee breakers and heavy drills sold in Europe and former British colonies, etc. The Wolf name was sold off about 20 years ago to an outfit in Nottingham who sold a variety of knock off low quality Chinese tools under the Wolf brand and got a really bad reputation for low reliability
On a brighter note some Wolf products were manufactured in India by a one time part owned subsidiary (?) called Ralli Wolf who are still in existence and still make a few of the old Wolf designs
