A revival of a three year old thread to which I did not make a response until now.
The key blanks in such knives were not universal. Even uncut, they were already grooved on one or both sides to fit a particular series of locks or ignition swithches.
If the knife handle had advertising for Chevy, GM, Ford, etc, the key could only be cut to fit that make car from the model year for which the knife was advertising. I'm pretty sure they were given away by the local dealers.
The key blanks in the Robeson knives were made to be cut to fit Yale post office box locks, but Robeson provided a free service to replace that Yale blank with one that would fit the owner's box lock.
If the writer of the OP in this thread wishes to have his house door key in his knife, he'll have to get a competent knife maker to alter his door key and install in into a pocket knife frame.
Robeson knife with Yale key blank in backside handle:
How to get the correct key into the knife:
Knife and key:
I've seen these Robeson knives in gold and silver finish and with different machining on the handles.
The two I have, one gold, one silver, came together in yellow flannel pouches in a small shipping box. Evidently, new-old-stock from some retail dealer. One of the knives had that yellow card attached.