M 636 Jobmaster

Hello , since many years I have been the owner of this rare brochure of Cat dealer Shephard . In the early sixties they constructed a rear wheel drive for the new 630A , 631A and even for the DW20 and DW21 scrapers . It would be the first twin engine Cat scraper .
I never read or heard about one that would have been sold . But there must have been sold some ! Who can tell us more about this application ? [attachment=29453]M 636 Jobmaster.jpg[/attachment]
The Netherlands , johan7