Found some documentation listing the two middle switches as the rounding switch (up fraction down) and the decimal switch (auto? 0 to 6 then hex?). No idea on the other two.

www.calcuseum.com/SCRAPBOOK/BONUS/32853/1.htm

Decimal switch: [A-0-2-3-4-6-F], Round switch: [(ArrowUp)-5/4-(ArrowDown)], Miscellaneous switch: [(Blank)-K .-(Sigma)],