The PG-200 is one of three Casio calculators in this style, dating from around 1983-1984.
Pachinko has been a popular game in Japan for years, kind of a cross between pinball and a slot machine.
The aim is to shoot a number of balls vertically up a lane (like shooting a pinball) and they then bounce around on pins/nails before dropping to the bottom or, if you’re lucky, hitting some scoring sections which allocate you more balls. A little bit like a grand version of a Bryans All-Win.
The calculator version starts with 50 balls and the only control is a button labelled ‘Lever’ — how long you hold the key down determines the force each ball is shot with and, to a certain degree, you can control where the ball will start its descent.
There’s not a whole lot of playability in it, although the sounds are quite fun, but it must have sold well in Japan since they made two non-calculator versions — the PG-100 and PG-500 (Pachinko 2).
For a while there were a reasonable number of NOS PG-200s that turned up on eBay so most people who wanted one at the time would have got one for a good price. They’re rarer now, and some have problems with the screen reflector degrading which makes it look bad and no fun to play, so still sell for a commanding price.