The Sperry-Remington 1100, introduced somewhere in 1975 and made in Japan, appears to be a rebadged Casio Pocket Mini (CP-801C), running as that device does on the NEC μPD974C logic chip. The Casio device had a memory function - the button for it was where the 1100 has its percentage button; the percentage button on the Casio was where the square root button is on the 1100. Other than that, it's identical.
It's 96mm high by 60mm wide, and 19mm thick. It takes 2 AA batteries.
It turns on by a sliding button on the left side of the device. It has a Vacuum Fluorescent Display (VFD), a type of display still used today in places that are subjected to abuse. You'll find them in cars, microwave ovens, and some handheld video games from the seventies. The technology includes phosphor anodes which can lose their potency over the years, fading the display. This one has faded only a little. A lovely calculator that fits in the palm of anyone's hand.
A lovely size. This device was produced just as LCD screens, which do not produce their own light and so use far less battery, were introduced. VFD had successfully been minimised, but was about to be replaced.