The first calculator I owned was a Sharp EL-506C (1981?). I loved that thing, but it died and I replaced it with an EL-506G, which I used into the late 90s. And now I need to dig it up again for use in a class I'm taking (phone calculators are not permitted for use during exams).

Looks like Sharp is up to the EL-506W model now, still recognizably the same lineage as your 5813 or my 506C.