It can have either a Walker 3 ton model 925 or the manual also lists the auto specialty brand. Here is a link to a thread that covers the jack:
http://www.mapleleafup.net/forums/sh...73&postcount=6
Auto Specialties was out of Windsor ON. Here is a link to a site about them:
http://www.internationalmetropolis.c...alties-mfg-co/
While Bruce states that the proper jack should have the large button on top, I note the manual drawings show the normal size button.
The Walker 925 is somewhat common, and was used both commercially and on many US military vehicles over the years. They have not been produced for quite a while, but rebuild kits are still available for them.