I don't believe anybody has taken up the trivia challenge about pioneers' marks of distinction, so I'll try that one.

In the British Army, each regiment of foot had a squad of pioneers to act as basic military engineers - cut down obstacles, etc, ahead of the regiments movements. They originated in the 18th century, I think. Then, their marks of distinction were a bibbed leather apron and a pioneer "cap" (similar to a grenadier cap, but much shorter and with a distinctive front-plate), as well as the axes, saws and shovels they carried (in addition to their muskets, bayonets and cartridge boxes). In the 19th c., pioneers continued to wear leather aprons and carry their tools, and were distinguished by being allowed to wear beards, in addition carrying their other distinct accoutrements - enlisted men in the Army were not then allowed chin hair, although their sideburns and moustaches were sometimes almost indistinguishable.

I have seen Canada's Fort Henry Guard (portraying British soldiers of 1867) perform, and they have a couple of pioneers who appear on parade. They carry axes at the slope and perform the manual exercise with them - present arms, port arms, order arms - in a very distinctive manner.

I cannot remember when pioneers were removed from regimental establishments, and it may be that some regiments still have ceremonial pioneers on parade as a remembrance. Perhaps one of you British Army experts can ellucidate me...