Sharp ELSI MATE EL-8109 Scientific Calculator
This Sharp scientific calculator appears to be rather uncommon. Based on the date code on the LSI chip that runs the machine, it is circa mid-1975. It is battery (4 AA-cell) or AC-powered (with an adapter), and uses a 9-digit (8 digits plus sign/error indication on the left digit of the display) standard seven segment VF tube for display. The display cover is tinted green, turning the blue digits of the VF tube a solid green tint, which is unusual.
It does not handle scientific notation, but does have a couple of unusual functions. It does trig (with inverse) functions in degrees or radians (based on setting of DEG/RAD switch); log(x); ln(x); 1/x; square root; ex; x2; and yx. It also has unusual conversions to take degrees/minutes/seconds (each keyed separately) to decimal notation and back. The [F] selects the alternate function for each key. The machine has a [π] key, and a single memory register, with memory recall [RM], [M+], and [x->M] keys.
The machine is controlled by a single Rockwell LSI chip, part number A4501PA, with date code of 7519.