When I was 16-18 back in 1969-71 I worked at a Ford Lincoln & Mercury dealership in Southampton NY. My job was detailing and cleaning up both new and occasionally used cars. New cars were kind of a mess with stickers/smudges on both inside and outside window glass. I had to spray glass-cleaner on each cars window sticker/soak, and peal them off with a single edge razor, lay out to dry, fold up and then into owners manual bag they went. I doubt many Dealers provided this service?
One thing that we did on every car is soak 0000 steel wool with Afta cleaning fluid and scrub through the clear lacquer like protective coating that the bumpers obviously were dunked in to get the transparent coating off. ( You could actually see and feel the runs where it was extra thick) Where the Bumper Bolt heads were there were always rings of the lacquer like protectant left around them where the steel wool was difficult to reach. Properly a showroom chromed bumper Mustang should have those protectant rings around all the bumper bolts. I assure you no new car prep guy would remove the bolts to get up close enough not to leave a ring..
If Concours Judging revolves around as: 'Delivered new to original owner.' There's no way a new Mustang or Ford, Lincoln Merc would have been delivered without these "lacquer" rings. I suppose at a sloppy dealer they might have not cleaned the protectant off all that well (like lower sides of bumpers). We were a high $ dealer and actually waxed every new car before delivery. No bumper looked good with that stuff on as delivered from FoMoCo to the dealers. It would stick out like a sore thumb.
I'm going to guess it was at least a 5-10 minute job per bumper - of course the stuff was on everything from Pinto's to Town Cars.
We used the Afta solvent mixed with motor oil to shine the vinyl tops... I only wonder how that affected the tops in the long run. We never removed/returned the chain down plates. Odd to think of today was a template in a bag with the radio antenna and we had to drill the five holes, mount the antenna and feed the wire in to the radio's on if I recall correctly every new car.. Odd in about 1 out of 10 cars I'd find a radio noise suppression kit (grounding straps, capacitor like jobs, copper cheese grater jobs etc) laying in the car - they never went anywhere except into the extra parts FoMoCo donated bin .
Maybe 1 out of a 100 had the Auto-Seat belt rollers (like a mini hair curler) Digging through my parts I found I have (4) NOS today
My Thursday job was to pick-up/return, detail all the cars from the Ford families estate on the ocean. (A rumor told to me by the shop mgr was Edsel put a car into the tall privet hedge that lined the long sweeping driveway to the estate.) The Ford's cars were almost all Lincolns, Mercury wagons and my favorite a black XL Galaxie, white convertible top, high back white buckets, auto w/console, styled steel wheels w70series and a Police Interceptor motor and Traction Loc I always presumed that was Henry's Car... Always made sure that Police Interceptor mill performed properly and would schedule the Galaxie's detailing around my lunch hour.