1st degree level 1 is probationary black belt, black belt with white stripe, no name on it.
1st degree level 2 is decided black belt, solid black belt with name embroidered on it and 1 stripe with a L2 on it.
(Both of these ranks most of you know as Gwang-Gae form)
1st degree level 3 and 4 (Ge-Baek form) have black belt with name, 1 stripe and either L3 or L4 on it.
2nd degree is solid black belt with name, 2 stripes and either L1, L2, L3, or L4 on it.
2nd degree Level 1 and 2 have the form most of you know as Yoo-Sin.
2nd degree Level 3 and 4 have the form most of you know as Ul-Ji.
3rd degree is solid black with name, 3 stripes and either L1, L2, L3, or L4 on it.
3rd degree Level 1 and 2 have the form most of you know as Choong-Jang.
3rd degree Level 3 and 4 have the form most of you know as Juche.
It is my understanding these forms were modified somewhat from their orignal Korean forms but are still very similar.