[Heathkit] SB-100 question

[Yong Surk Lee]

I just obtained a SB-100 in very good condition from a local ham here in Korea. Could someone answer me the following questions?
1. Difference among 100, 101 and 102 models.
2. Time period 100 model was made.
3. Which tubes in 100 need to be shield capped? It came with only 3 tube shield covers, one is 9 pin long for 6CL6 i believe, another is for a 7 pin short tube and the last one is for a 9 pin short tube.
Thanks in advance.
de HL1FB