Visto

08:22 Jul 11, 2019 

Thank you everyone for putting me on the right tracks. I think the idea of "visto" as Chema says is more akin to the charateristics of the surface like "ladrillos visto o caravista" EXPOSED BRICKWORK (FAIR-FACED BRICK) as well as its purpose. So I am going for Exposed Plexiglass.

18:26 Jul 9, 2019 

I understand your point, Simon.
Check out this example though.
Las letras corpóreas retroiluminadas con metacrilato visto están fabricadas por un frente de latón soldado a los laterales de latón y cerradas por la parte trasera con un metacrilato de 10 o de 20mm para el efecto retroiluminado.
https://www.letracorporea.com/es/ficha-modelo/retroiluminado...
They are talking about brass letters (front and lateral) with an acrylic layer on the back and the posterior side of them. The "interior" of the letter is illuminated so that you see a brass front and an halo effect as you can see the light coming out of its side through the acrylic. Check the image -and do please excuse my effortful English here. The acrylic is "at view" even though it is not up front.

12:56 Jul 9, 2019 

You may be right, but "Las letras corpóreas retroiluminadas con metacrilato visto" - in my opinion means that as the letters affixed to, or made with, the "metacrilato visto" are back lightened "retroiluminadas", the material, "metacrilato" must be "transparent" in order to allow the light through.

Your ref. is "at view" or "apparent", and in this case would mean that the "metacrilato" can be seen, which can or not be the case here, depending if it is colored or not.
Maria's comment does not address the question of "visto".

11:36 Jul 9, 2019 

I agree with Chema's explanation. Maybe raised acrylic is another option:LED Backlit Glow Signs - Signage
www.signagekraft.com/index.php?route=product/category&path=...
LED Backlit Glow Signs. ... SIGNAGE WITH BACKLIT 12MM ACRYLIC LETTERS ... SIGNAGE WITH BACKLIT RAISED ACRYLIC LETTERS .

23:08 Jul 8, 2019 

Tal vez haya formas específicas de describirlo en inglés. La idea de "visto" en cualquier caso es la de un material que queda a la vista. Ver por ejemplo "ladrillo visto": https://www.google.es/search?q="ladrillo visto"&tbm=isch&ved...