The form "Wefsel" is actually found in older German records (including church records and family Bibles) as "Weƒsel" where the letter ƒ is just another way of pronouncing the "hard s" sound. The "ƒs" are always found together, somewhere in the middle of a word. (You can create the "ƒ" by holding down your ALT key and tapping 0-1-3-1 on your keypad).
The combination of "ƒs" is also found in handwritten English orthography (same "ss" as in German) in the 1600's and 1700's. It faded from common usage by the end of the 18th century.
As you know, the single German letter ß represents the English "ss" but it is found at the end of the word (quick example: Elsaß = el-zass = Alsace, the French-German border province). You can create this one by using ALT + 2-2-5.