Let me make a correction. I think Charlie meant the snafu was the bracket falling off. The pickguard binding on the mandolins do not get varnish on them so they will be the actual color of the binding material. On the Fern we use a white plastic, but the varnish turns the color this really warm ivory color. Since the pickguard is not varnished, and would not do well with the finish on it, the pickguard is the white color.
The Master Model uses an ivoroid binding but is also varnished over retaining the warm ivory color. The pickguard binding is the same as on the fern. White binding. The originals were similar to this.
Now, to the matter of construction differences from the Varnished Fern to the Master Model. The fern uses the same construction and materials as the standard fern. The only difference is the varnish instead of lacquer and, of course, the price. The Master Model uses a red spruce top, hide glue, macasar ebony under the fingerboard extension, flowerpot (on most MM's) and only available in varnish and french polish finish.
Tonally the MM will sound more loar like than the fern. The fern will have a slightly darker sound than the MM. They will both play similar and there is some variation from mandolin to mandolin. These are kind of generalizations on tone, but seem to be true in all that I've seen. The Varnish Fern is not a standard production item and is only available from time to time. They are exceptional values and the sound is incredible. It is impossible to make many so one must make hay while the sun shines . One final word. There is generally a varnished fern and a master model at the Bluegrass Showcase you can play and check out. We try to keep both on hand all the time.
Have a Great Day!