Thank you to Kei Braun who solved a really tough one. We gave up trying to identify this wheel, which is definitely from a Saab, but with slight differences. He found that it is from a VERY early 340; read Kei's comments below.
 
"I tried tracking down cockpit photos of very early prototype model SAAB 340's to no avail. However, I came across a report (https://www.icas.org/icas_archive/ICAS1984/ICAS-84-2.5.1.pdf), copyrighted 1984 (which was the commercial launch year of the first SAAB 340), authored by Fairchild (which went bankrupt soon after production began) which showcased program development, design, and key features of the aircraft. This report is from the very initial stages of the 340A's commercial run, and must've used details from prototype airframes (due to it being copyrighted in 1984, only months after its first flight in 1983). Within this report, I found the jackpot: