HP-10S+ Scientific Calculator: is it a CASIO clone?

[jebem]

A local store is selling this HP-10S+ model since a couple of years ago and every time I pass by I'm tempted to buy one to join my collection.
I already have its big brother HP-300S+ and they complement each other with their excellent design and looks.

So I started searching for information on this model and found out a few intriguing reports. This was a good excuse to drive to the store and buy one to have a look myself.

Several people using this calculator since it came out in 2012 have commented that it looks like a CASIO clone, based on the fx-82MS, or on the fx-85MS, or on the fx-300MS.
Part of those comments are based on the fact that most of the features found in the HP-10S+ are identical on those CASIO models and even the menus are identical.

See here some of the reports:
Edward Shore - Caliber Scientific Calculator by CVS Pharmacy vs. Hewlett Packard HP 10s+
HP Support Forum - HP 10s+ screen contrast
Matheus Cariús - HP 10s+ copycat of CASIO fx-82MS
MoHPC forum members

However I'm not so sure about HP-10S being a clone of the CASIO's.

I share the statement of George Litauszky from MoHPC (see the link above) that both HP and CASIO shared a common software base developed by Kinpo TW in China and compiled to run on distinct hardware platforms.
This would explains why both have the same menu structures and many common functions.

One argument in favor of a CASIO clone:
The following test reported by BartdD on the HP Support Forum and by Matheus Cariús would tell us that the HP is a CASIO clone, because there is a leftover coding hidden in one of the HP menus that will display the same "CASIO" string found in the CASIO models to adjust the LCD contrast.

To get this "CASIO" string on the HP-10S+:
Press MODE four times and you will see DISP and a single option "1" below it.
However the CASIO's models have another option "2" to adjust the contrast that it is not available in the HP.
Now press 2 on the HP: The top row will show < LIGHT DARK> and the "CASIO" string below it, exactly like what a real CASIO does. However the HP-10S+ contrast adjustments seems to be inoperative and the user guide doesn't contain any references to contrast adjustment.

I have duplicated this test and got the same "CASIO" string on the non operative LCD contrast adjustment menu.
My calculator HP product is NW276AA#B10, Serial No.9CJ60300S0, Product of China.




Why I'm not so sure about the HP being a CASIO clone:
I realized that there are no forensics tests published for the HP-10S, HP-10S+ or HP-300S+ in the excellent Mike Sebastian listing.

Therefore I have run the usual arcsin(arccos(arctan(tan(cos(sin (9)))))) test and got a result of: 9.000000002123857

None of the CASIO models listed have this HP signature result.

By the way, the HP-300S+ forensics result is: 9.000000000881497
Again, no CASIO models listed have this signature.

I don't want to jump to conclusions, but it seems that the HP is using a distinct processor and hardware platform from what is used in the CASIO's.