Ventron

VT-600

This is a rare one from early days. Big and bold. Note that it only has a 6 digit display, but calculates 12 digits. The U/L switch lets you see the "upper" and "lower" 6 digits of the entire number.

Note: this powers off 5 AA batteries, not 3 as most every other source will tell you. They are quoting from the authoritative "The Complete Collector's Guide To Pocket Calculators" by Guy Ball and Bruce Flamm, but somehow the authors got this detail wrong. Inside the battery compartment is a tethered clip that holds two batteries on one side and 3 on the other.

This one was dead so I sold it in early 2013 for $50.