Dollieh Sanctuary

what is the difference between an SD and SD13?? anyone know what little monica enrill type A body size is?

Sd and Sd13 are usually used interchangeably unless you are actually looking at the Volks website. Officially the difference is that SD dolls look a little younger and are about 2 cm shorter than SD13, who have a slightly more mature teen body. Most places call SD dolls SD10 too.
Not too familiar with Little Monica dolls but if you can find the body's measurements on their website, you can compare it to Volks measurements and have a better idea of what will fit your doll.

Mainly unless you are talking Volks, it is used to differentiate between the 58-60 cm range of dolls (SD13) and the 65-70cm range of dolls (SD 17).