Hi beadwindow, my AAB journey started as I thought the Credit Lamp in the apron was not working and ended in my wiring a DIY "Added Ball Kit". My Rocket III is now switchable between Replay and "Shoot Again" (- which is what it says on the backglass). Yours will be very similar but I don't see a a lamp in the apron.
I have since found information in the 1969 Parts catalog that this conversion kit approach started with Rocket III
The chronological games list then highlights clearly those earlier than Rocket III had an AAB model * and later that were convertible using AAB Kit **. (All machines until Cosmos apart from The Wiggler for some reason)
I worked out the wiring for the Relay from the Schematic, I'm happy to help with this if needed.