Darp speed pans are ones that are still made, smallest for 2.5CC engines for FAI F2A
http://www.ayrproducts.com/pans.htm for a photo.
MJD description is right on but a photo will help.
Many years ago I used to buy speed pans from SIG - Tatone brand. That was back when control line flying was very popular.
Someone made a statement the other day that I found interesting - "Today, there is more spent each year by the RC crowd on servos alone than all of what is spent on control line flying". I don't know the source of this statistic or whether or not it is true, however it does have a ring of truth to it.
cheers, Graham