Cheapest Scientific Calculator?

[Chasfield]

Maybe the calc. is one of those ubiquitous 56 function scientifics. They appear in hundreds of guises and are all based (I think) on an old Sharp ROM.

These devices are quite nice to use, with old-school, post-fix operation for scientific functions but keyboards are likely to be a single-piece rubber membrane.

Since they can be had for less than the cost of a cup of coffee, you can take them anywhere without fear of loss.