My source is not "mysterious", I've kept saying so, and again in my last post. Is it only me who is seing the similarities between this long motorhome and the smaller vehicle of my puzzle? The bumpers, espescially the rear bumper, the shap and arrangement of windows and windshield. I could say the headlights setup but it's not easy to see in the profile photo of the bigger one. There are some elements not unlike Hunt' cars, yes. But his Turtle carries a decorative molding placed lower. When both these vehicles carry one just below and over the side glass.
The big one is attributed to Stevens by SIA. Stevens is noted by SIA as the possible author of the small one.
While Otto and Paul Jaray made earlier correct but unsure guesses, I think its right to give that point to Allemano who found the only (in my opinion) conclusive evidence sofar.
As it was a two points puzzle the second point is still at stake for whomever achieves to lift the veil.