Radio Shack (Tandy Corporation) was well known for selling under their own brand calculators made by other companies. Among those is this EC-4001 which was even made in the UK and relabeled EC-4001. But it is 100% the same as the Sinclair Programmable. The calculator is not very common in the US.
This particular one is brand new in its original retail box which is indeed a rarity! Being new, never used, the writing is intact and the keys are also not faded – both are real issues for this type.
It is accompanied by two manuals (User’s Guide and Program Library), same as the original Sinclair only that the Library manual is a much smaller format and is one volume only while the Sinclair comes with multiple volumes.
I have tested summarily the calculator, it works with a standard 9V battery.