I think I know what you mean by a builders kit. If it has a metal case that holds the 5/8 HP Stanley router and the planer attachment with spiral blade then I had the same one many years ago. I actually had two routers, one was given to me by another carpenter that was trying to sell some of his tools. I bought several tools and admired the router. Pete said take kid , this one is free. Long time ago , now I'm the 77 year old "kid".Guys I have stumbled across a complete(I think) stanley 91297-5 builders kit. To be honest I have no idea what most of these parts are for. I know that there are door attachments and a whole bunch of other attachments and related items. There is even the manuals parts lists and all original paperwork.
What do you guys think it is worth? Also is there a way to date the kit?
I do not know what it is worth , but I hung and fitted at least 300 doors with that kit.
I gave the kit to an apprentice after I retired. As far as I know he may still have it.
I received the kit on my birthday in 1966. I don't recall other attachments, probably a hinge template, lock strike template too. I do not think I used the hinge template much or at all since I always used the PC folding hinge template.