Most attitude indicators at the time only showed a single horizon line so Sperry had a choice as to how to portray the sky/ground image on their instruments. Their choice did not end up becoming the industry standard
Wonder if it was the pilots first time with a Sperry AH, doubt any of us would keep the greasy side down if it was presented to us, the Crossair accident pointed out by
B2N2 shows how quickly it can turn to worms when using an unaccustomed instrument.