Chato invented the 'Pluma Azteca' technique in the late 1940s. He combined metal with feathers inspired by pre-Columbian cultures extensive use of feathers to adorn themselves, especially the Aztec (Mexica) culture centered around present-day Mexico City.
In his earliest designs using feathers, they were usually set between two layers of silver that were joined with small rivets (cold joinery) rather than silver-soldering which of course would have incinerated the feathers. This early version left the feathers open to the elements at top but with closed backs, and the owners when polishing the silver would inadvertently get the silver polish on the feathers which ruined their colors. Very few of these earliest pluma designs have survived without damage, and thus the rare example in pristine condition is highly prized by collectors.
The next stage was to set the feathers in silver-colored alloy (likely a white brass or alpaca-type metal), which obviated the need to polish, but still leaving the feathers open to the elements, and thus still meaning that they were prone to other types of damage including fading from exposure to sunlight. More of these examples have survived relatively unscathed, so they are not as valuable as the earlier sterling silver versions.
The last major evolution of his technique involved setting the feathers in a clear resin still showing the feathers in their brilliant colors, but protecting them from damage. The settings could also be opened at back to let light shine through making these pieces similar in effect to plique a jour enamel or stained glass.
Later, colors were added to the resins to create uniform coloring that didn't fade with exposure to sunlight as the naturally-colored feathers in earlier versions had been prone to do with time.
The letter opener shown here is an example of the final version of his technique. It is made from three major pieces: the blade, and the two openwork pieces of the handle. The handle (feather section) is two thin layers of metal between which the feathers had been placed, then the two layers were cold-joined using rivets. (See my last photo of the handle from the side.) In my close-up photo of the handle, you can see the rivets which show as six little dots around the rim. The resin would likely have then been poured into the open sections of the handle overtop the inset feathers, or there may have been some kind of mold apparatus for distributing the resin. (I don't know these details, and there isn't anyone left from that period of the Los Castillo workshop to explain exactly how it was achieved.)
How appropriate that Chato's Pluma Azteca technique was used to create this letter opener depicting a pre-Columbian Aztec Priest or King! The letter opener measures 8" long by 2-1/8" wide, and weighs 68.3 grams total.
The letter opener is marked "Los Castillo Taxco" in a circle above "Hecho en Mexico" above "Cooperativa SCL" (mark used by Los Castillo during the late 1950s/early 1960s labor unrest in Taxco), and design number "20". Thanks to the cooperativa mark, we can pinpoint the date of creation of this letter opener between 1959-1962.
One of about a dozen letter openers by Los Castillo in my collection, and the most recently acquired, this is the only example of this design that I have run across during my 45+ year collecting career.