I've looked further at this year old question. They can still be earned in TD1 and still show up in TD2. They are arranged in tiers, each tier giving you something. I personally think that the SHIELD's gave better benefits to TD1 while playing it than TD2. You get the following for TD1 for each one (that's a lot of "slow to earn" Div Tech):
- One Audio Log
- One Patch with the relevant Shield Icon
- One Shield Cache
- One Exotic Weapon
- Two Classified Gear Set pieces
- 2,000 Phoenix Credits
- 500 D-Tech
- Three Cypher Keys
Refer to:
https://support.ubisoft.com/en-US/Fa...ivision-2-TCTD
and
https://www.ubisoft.com/en-gb/game/t...the-division-2