The HP-41 Blanknut version is a variant of the HP-41CV made by HP for customers who needed to sell the calculator bundled with their own software. The calculator is definitely the least common version of the HP-41 family.
One of the most frequently seen Blanknut versions is the one sold by GE Financial together with “GE Financing” module. There are three known versions of this module.
The Blanknut calculator does not have any labels on some keys, two of the keys from the upper row (USER and PRGM) are covered by a plastic piece and the mack label is usually missing but labels.
The box is also different:
The box itself lacks the HP-41 designation as it can be seen in the image.
Here is how a Blanknut calculator looks like:
This particular calculator has had corrosion on its battery terminals and is now non functional but still an interesting piece to display. Additional images: