HP 41 - Strangeness

[Thomas Okken]

That type, officially called "Option 001" but more commonly referred to as a "blanknut" in this forum, was made for customers who wanted to run special-purpose software on it, using keyboard overlays to indicate the keys' functions. Apart from the missing legends, it is a regular 41.

I don't know which of the 41C, 41CV, and 41CX were made as blanknuts, but you can tell them apart easily: first, with the calculator off, remove all modules (if any are inserted in the expansion ports at the top end of the calculator), then turn it on while holding the left-arrow key. You should see MEMORY LOST in the display. Then, type [RCL] [1] [7]. If it says NONEXISTENT, it's a 41C, else it's a 41CV or 41CX. To tell the difference between CV and CX, press [Shift] [CATALOG] [2]. If it's a 41CX, four items should be shown: TIME 2C, CX TIME, EXT FCN 2D, and CX EXT FCN; if it's a CV, the catalog will be empty.

(Updated because of errors in how to tell apart 41C and 41CV.)