Slot, as you can see, I got much the same actuator, except my solenoid is visible out the back...picture showed up smaller than I thought...I'll get a better one soon...
I'm like you, I really like this unit, specially the locking pin you mentioned...
...and thanks for the vote of confidence and YEP, I do want mine to look like that 8) ...good stuff, Airslot ;) ...