...or pictorial hardbound covers.

Every one of the books of this type that I looked at had an illustrated cover (not a dust jacket, that's "sobrecubierta"). Since "cromo", according to Collins Dict., can mean "picture card" or "colored print", that makes sense.

Here's an example (there is a nice photo of the book):

Ediciones El Viso ha cuidado hasta el más mínimo detalle la encuadernación de los 1000 ejemplares que conforman esta primera edición, realizada en cartoné al cromo, proporcionándonos no sólo una obra literaria de agradable lectura sino, también, una verdadera obra de arte.
http://www.actualidadambiental.com/frameabajo.asp?pagina=ven...

Here is some info. in English.

Panels or boards-- hard covers for front and back sides of book.
Pictorial-- picture on the cover.
http://www.bookuse.org/Glossary.htm#Embellishments

There are photos of the books at the links below:

***Hardbound. Pictorial cover*** is the same illustration as on the frontispiece.
http://www.findgreatstuff.com/books.html

240 pages, ***hardbound, pictorial boards***, small format
http://danwebbbooks.com/SS-Steel.htm

48 pages, ***pictorial hardbound covers*** in fine condition.
http://www.waterrow.org.uk/motoringbooks/Mercedes_Books_page...

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Note added at 6 days (2007-11-06 06:51:45 GMT)
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No, I don't think "lámina de revestimiento" refers to a dust jacket (as I said, that's usually "sobrecubierta")--although there's only one reference on Google in a book context, so it's hard to tell for sure. I think it's a way of saying the boards are laminated, which is quite common. Have a look:
http://www.google.es/search?hl=en&q=book hardbound pictorial...

In any case, if you really have reason to believe it's a dust jacket, it is also not uncommon for books with pictorial covers to have a dust jacket with the same picture. See:

Full page color illustrations, color and black and white in-text illustrations, color pictorial endpapers, unpaginated, 10 x 7 1/4 inches, ***color pictorial paper-covered boards in color pictorial dustjacket***.
http://www.oldimprints.com/OldImprints/Children's_Illus...

...original blue coloured ***pictorial boards, matching dust-jacket, (in mylar)*** a few light marks, some very light staining.
http://www.cambridgeprints.com/catalogues/cartoonists.htm

Oblong 4to., ***pictorial boards,*** the transformation of a "gloomy" woodcarver, very good in ***matching pictorial dust jacket.***
http://www.ilab.org/services/catalogues.php?membernr=1731&ca...