As promised: Here are images of the (presumably) original locking system on my Callen camper. Check file names for orientation (interior, exterior, left, right, top, base...)
I've owned this shell for 13 years- bought it for travel in Baja along the coast (note: rust!) after Leer shells on previous trucks leaked dust and/or showed stress fractures in the fiberglass after bouncing over rough roads to get to/from the coast from the Central peninsula while carrying gear on Yakima racks.
It's one of those "They seriously don't make them like this anymore" objects.
- Steel frame under aluminum exterior, insulation under the retro wood paneling... it's like crawling into an comfy old fallout shelter from the Cold War era to get out of the wind and rain.
They were built by the Callen family in the 50s El Cajon. Owners often share stories about how they love them and will pass them on to the next family generation of overlanders.
I still see many in San Diego - it may outlive me

(and will certainly outlast my 25 YO B-4000 Mazda truck)
PS- The smashed car is what happened when a tailgater along a wet, muddy Hwy 1 in Mexico hit me as I waited for the red light in the background to change. My truck & the Callen (see images of this in my initial reply) were basically unscathed... theirs appeared to be totaled.