I used the key from my 84 Accord to get into my 98 Integra when I locked the keys in it. Similarly, my 89 Accord would unlock using pretty much any other Honda

I used the key from my 84 Accord to get into my 98 Integra when I locked the keys in it. Similarly, my 89 Accord would unlock using pretty much any other Honda key. One day, I locked myself out of my 81 Accord... but it uses the short, old school style Honda keys, so I didn't have another car to take keys from to try... so I called a locksmith. He comes out and goes "Oh I haven't done one of these in a while..." pulls a blank key out of his toolbox, sticks it in the door tumbler, and opens it right up. So now I have an 80 and an 81 Accord... and I have also interchanged keys between them. The 80 doesn't open as easily, as I think it's less worn out. But there's practically no security on these old Hondas.