I bought a Heuer Bund from a collector a year or two ago, and was told that it was from the Sinn Collection. It has the same number the caseback, but The Bund writing is different. Would be interested in understanding the difference. I was given the Sinn letter and instructions on this watch as well.

In case anyone is interested, I might consider a trade or sale, but for now, I am just trying to gather some info, since the topic of this same watch came up.