This is information given to me by different sidesaddle riders. Please chime it if you have anything to add!
1. Sidesaddles are girthed up on the off side.
2. A Royal Warrant is a possible mark on the saddle with "By Appointment to [insert name of member of royal family here]". A company or individual who has provided goods or services to a "royal" that way can apply for the Warrant, which is good for a certain number of years and can then be renewed. It's great advertising, and of course still used--look in any Barbour coat! Anyway, if a saddle does have one, depending on whose name is given as the granter of the Warrant, it helps determine the earliest and latest years when a saddle could have been made.
3. The Impakt saddle pad is made out of some kind of foam. It feels weird, almost sticky. When it heats up from the horse's back it adheres to the back and also the saddle. I should say it adheres to a leather saddle, it wouldn't do the same with linen. After a ride I would carefully peel the saddle off the pad, then the pad off of the horse. The pad was always wet, but Marcel's back was always dry. It held the saddle where I put it without having to tighten the girth as much as you normally would with a sidesaddle. It did well with his wedges too. The felt has a bit of grip to it to hold the saddle and they never budged off the pad.
4. "A Queen" is a foam cushioning covered in sheepskin (can be faux) on one side to pad the fixed head. Extra wide elastic, 2" - 3" is used on the other side.
5. I have also learned how you girth up your sidesaddle TOTALLY depends on what kind and even what brand of sidesaddle you own. There are as many answers to this question as there are saddles! Uggghhhhhh!