The mythical LP typewriter key

I had always thought it was a myth. When Columbia Records debuted the vinyl Long Play record they held an international contest to name the format. All submissions were rejected and it was crowned formally with the term it'd held in house informally all along: the LP.
They were unable to patent the format as it contained no new technology, but they could trademark the name LP. So they did. I have written often of the ostentatious platter. Here & here. The story is that in the late 1950s Columbia had the office typewriters re-keyed to have an LP key. I have confirmed this somewhat by the single reference in the book "The Label: the story of Columbia Records" by Gary Marmorstein put it back on the table.

Gary asks the question I have asked myself "Which key was removed to make room for it?"