Most older pre 1995 Genie garage door openers used a fixed code 12 switch remote like the two position block shown below. Matching the switches in the remote to another working remote will set your code your code. When you do not have a working remote match the switches to your receiver on the motor unit hanging in the garage. This remote includes battery, key chain and programming instructions.
The Firefly3® remote works with Genie 12 switch versions of garage door opener remotes on the 390MHz frequency.