Firstly a link to the catalog
https://www.ragandbone.ca/PDFs/Miyat...logue%2085.pdf
We know it's an '85 based on that seat tube sticker, they changed every year. In '85 Miyata measured their touring bikes in inches which makes them pretty easy to size. Looking at the head tube length I know it's larger than a 21" frame and smaller than than a 25" frame so it's a 23" frame.
23" = 58.4cm, Miyata measures seat tubes from center of the BB to top of the top tube, so center to center its a little bigger than a 57cm.
At 6'1" the "will it fit" question depends on your cycling inseam length, your fitness and flexability, and your fit preference. If you carry your hight in your torso it could be a good fit, if more of your height is in your legs, it could be too small.
If it fits, I think its worth picking up. I had an '84 610 and it has clearence for 40mm tires (without fenders) and it's nice and stout. It flexes less under load than the Trek tourers, at least less than my '83 Trek 720. They have 45cm chainstays, and the canti brakes can be adjusted to reach 700c wheels (again based on my 23" '84 610).
I find that for whatever reason Miyata's tend to ride a little smaller than their stated size, but I have measurements a little outside of average. I am of average height but more of my height is in my legs than in my torso, and I tend to larger frames because of it.