My '65 Cutlass came with only 2 keys.
The trunk key looks original, but what
about the door and ignition key.

 

The Oldsmobile crest key is aftermarket and was actually pretty common. I haven't seen one of those DAV license plate key tags in years, always thought they were cool. Trouble was, you lost your keys, all the thief had to do was find the car with that plate and gone.

A good locksmith will usually have original GM Briggs & Stratton key blanks even for the older cars. The original keys had a knockout lug in them with the original key code number stamped in. Locksmith can make them either from that code or by using a key cutting machine.

FWIW, all 1935-1966 GM key blanks are the same. Original ignition and door had an octagonal head, trunk/gloveboxes was round.

 

Stop whatever you're doing and go get copies of those keys made or Murphy's law will kick in, don't need another "How do I open my trunk with no key?" thread. At least chain a brick to them.
If you have it the owner's manual should show some key stuff, the Fisher Body manual goes more in depth.
In any used GM car I got I punched those key codes out and threw them away, they made the keys bind up on the ring.
I have one of those mini plates on my key ring right now, I used them on all my Tonka trucks and changed them out for the new ones every year.

 

I had keys made when I bought it back in 1999.
But if I had to open the trunk I would use the
trunk release in the glove box.