similar in style to the sr-4148r,
this model has a similar function set having two memories, exponent
ranging and stats and dates from around 1976.
one significant difference is the vacuum fluorescent display rather
than *led*. these are larger and clearer making them easier to read.
oddly, this model will only display 8+2 digits (the sr-4148r
is 10+2) but underneath it is actually a 10 digit machine, having 12
significant figures internally. so when no exponent is present, the right
two digits are blanked rather than be used to display a 10 digit result
(there are actually 12 digits on the vfd).

it is identical in function to the desktop model
1540 having the same chipset and giving identical answers.
interestingly, the 1540 displays the full 10+2 digits and displays a ten
digit result when no exponent is present. the 1540 is also slightly
faster.

there are only 39 buttons, so unlike the 4148r's 48 keys, a shift key
is required, designated by *F*. operation is straightforward and
there are some useful touches, like the *ee* exponent ranging, *d-r*
which switches mode between degrees and radians and also doubles as a
converter. brackets are only to one level and there is no operator precedence
(eg 2+3*5=25).