We like to believe that metal planes cornered the market on the ability to adjust the size of the throat opening, but this is not the case. Here is a German plane circa 1895 from german plane maker Georg Ott, Ulm/Germany (“Ulmia”). It has a German utility model number 21788 (couldn’t find this online anywhere as it is different from a patent). It was issued in 1894 for a plane type known as a Reformhobel (reform plane).
The plane had a removable “shoe” which was used to adjust the throat of the plane, and adjusted using a machine screw. Interestingly the sole itself had five layers: a lignum vitae sole, two layers of apple wood, a steel plate to which the machine screw attached, and a layer of sandpaper to reduce slippage of the toe. Below is a picture from an early Ulmia catalog (labels modified to English), which shows the adjustable throat mechanism.
Strangely enough, it must not have been popular, because none of the contemporary planes seem to have an adjustable mouth.