I emailed back and forth with a very helpful researcher from Westerbork, who couldn't find any record of a Henry Wertheim ... so I sent a copy of the postcard, and it turns out that the first name on the card is actually Heinz.
They were able to tell me that Heinz Wertheim was a shoemaker apprentice who was born on June 26th, 1921 in Bremke, Germany. He married a Dutch girl named, Ruth Sara*, and they lived in the Netherlands and were sent together to Westerbork. They were so young ... he would have been 22 and and she just 21.
In Westerbork, on May 6, 1943, they had a baby and named him Paul Freidrich.
The baby died six weeks later.
I just noticed that the postcard was written on May 5th 1943, the day before the baby was born, and postmarked May 8th, two days after. Perhaps they got money from someone outside Westerbork because they were expecting a baby (the postcard said, "Many thanks for the money you sent.") ... and I imagine Heinz wrote the card on the 5th, then was busy with the new baby and didn't get a chance to mail the card until the 8th.
Shortly after the baby died, on September 14, 1943, Heinz and Ruth were sent together to Auschwitz.
Heinz died at Monowitz, which was a labor camp at Auschwitz, on December 12, 1944, after surviving there for more than a year. He was 23. His wife, Ruth, survived Auschwitz and was sent to Ravensbruck and then Malchow, a subcamp of Ravensbruck. She survived the death marches from Ravensbruck before being liberated in Neustadt. She eventually emigrated to Israel.
There's one more thing.
I think Ruth may still be alive and that I've possibly located her. She would be 88 now. I have probably the only thing that still physically exists that her young husband touched ... all those years ago, right at the same time their baby was born.
So, do I leave well enough alone, or try to contact her and ask if she wants the postcard?
*During the Holocaust, Jewish women were made to use the middle name "Sara" to state their Jewishness. I don't know if this is her real middle name or not.
18 hours ago