Hi Michael,

Thank you very much for your deep answer.

As recommended by you, i made another and more precise test and here i present you the result.
My Rhino version is : Version 5 SR12 64-bit 5.12.50810.13095, 10/08/2015

I have attached the 3dm files and the screen captures of all the test stages.

This are the steps of the test i made :

1) Step 001
Create a simple file in Moi that contain only 1 sphere, named "sphere1" and assigned to a material named "moi_sphere",
then saved it in the file "step_001_saved_from_moi.3dm".
See the attached files "step_001_saved_from_moi.3dm" and "step_001.PNG"

2) Step 002
Loaded in Rhino V5 the file "step_001_saved_from_moi.3dm" and assigned a marble material to the sphere.
After that i first wanted to overwrite the file, and Rhino showed me the popup window captured in the "step_002_B.PNG" file.
The popup said : "This model contains information that cannot be saved in the Rhino 4.0 file format.......Save as 4.0 file.....Save as 5.0 file....."
Anyway, in order to maintain separated the steps of this test, i saved as 5.0 in the new file "step_002_saved_from_rhino.3dm"
See the attached files "step_002_saved_from_rhino.3dm" and "step_002_B.PNG"

3) Step 003
Loaded in Moi the file "step_002_saved_from_rhino.3dm" and simply added a new object.
A cylinder assigned to a material named "moi_cylinder".
I didn't touch the sphere.
Save all to the new file "step_003_saved_from_moi.3dm".
See the attached files "step_003_saved_from_moi.3dm" and "step_003.PNG"

4) Step 004
Loaded in Rhino V5 the file "step_003_saved_from_moi.3dm" and duplicated the cylinder made in Moi.
The marble material assigned to the sphere was always there.
I didn't touch the sphere.
Save all to the new file "step_004_saved_from_rhino.3dm".
See the attached files "step_004_saved_from_rhino.3dm" and "step_004.PNG"

5) Step 005
Loaded in Moi the file "step_004_saved_from_rhino.3dm" and this time simply moved the sphere object.
That's the crucial point!
Save all to the new file "step_005_saved_from_moi.3dm".
See the attached files "step_005_saved_from_moi.3dm" and "step_005.PNG"

6) Step 006
Loaded in Rhino V5 the file "step_005_saved_from_moi.3dm" and....
THE SPHERE OBJECT HAD NO MORE THE RHINO MATERIAL ..
See the attached file "step_006.PNG"

So....is it all correct ? Is this the normal behavior of the entire process ?
I ask this 'cause i want to know a good workflow method to follow in order to use both the software, Rhino and Moi.
Just to model both in Moi and Rhino, save back and forth the files, and then render all inside Rhino/Thea Render.

And...about the other question i made, regarding the writing of the search/history commands plugin,
i'll will try to use the <moi:TextInput> instead the standard html <input>, as recommended by you.

Compatibly with my work commitments, i hope that soon i can post some decent lines of code.

Meantime...thank's again for your support and...good night!

Marco.