I have two similar calculators that were giveaways from companies. If you peel off the price tag, you might find a company name. One of mine is labelled Mitel. All the package says is 'Made in Hong Kong'. The other is from Northern Telecom. The model might be 'Grand Prix'. It was imported by Lidco in Markham, Ont. Mine are both ancient - maybe 20 - 30 years old.
No idea what chipset was used. The thing is so thin that it must be a COB (chip on board) construction so it would be covered with an epoxy blob. For anyone reading this, these things are the size of a credit card and about 2.5 mm thick.
Why do you want to know the chipset?