All About Pocket Knives

I've had this broken Imperial jack knife since forever and know nothing about the ID. The tang stamps are extremely difficult to make out. The broken main blade is "Imperial" and under that "???? USA". What is left of the secondary blade is "2176637" ? to the left side of that is a "P" ? and under that is "261782"? It is about 2 5/8'' closed (like a peanut); the covers are metal, and the shield is plain. What is left of it stays very sharp and finds occasional use in cutting hoses and such (just to keep it useful). I know that is not much to go on, but any help in ID would be appreciated.

Those numbers are patent numbers, they aren't model numbers or date markings. I'm not the right guy to help you date it, but I'm betting one of the experts will probably be along to help.

Here's a tip for photos: Turn off the flash and provide adequate indirect ambient light. The flash creates the glare & reflections that wash out the stampings.