I needed to test a Sol-20 keyboard on an Replica 1, which uses the Apple-2 interface. Since the unified keyboard project encoder has connectors for Apple 1, Apple 2, and Sol-20 which are all connected, I was able to use a bare encoder board as an adapter.
Since such an adapter is handy, and I haven't seen a readily available free design including the design files, I chopped off the encoder portion of the board, and the result is an adapter tha can be used to connect an Apple 2 keyboard to an Apple 1, or vice versa. I include proto-board style pads for flexible selection of on-board RESET and CLEAR switches, and a connector for external RESET and CLEAR.
You can download the design files from
Here's a rendering: