The Presiding Overseer told me that the second one if a secondary corporation in charge of the legal department for the WB&TS.
Eventually they wanted to distance themselves from the idea that a corporation was in charge of God's earthly organization and started sending letters from "The Christian Congregation of Jehovah's Witnesses
Truth B Known
You said you were 15 when you saw the letter heads on the two letters. Out of interest, what year was that? and do you know when they started using the letterhead 'Christian' congregation of Jehovah's witnesses