?
The FM: Periphery was written after the Capellan Civil War and it said nothing of them sent to St. Ives and wrote that they were still employed by the TC. The Mercenaries: Supplemental Update says the Valkyries were fired by the time the FM: Periphery was written.
How can they both be right? When exactly was the unit sent to the war?
You didn't mention that in your original question. Newer sourcebooks override the old, so MSU version is correct in that they fought on Texlos in 3061 and then got fired by the TC. It doesn't invalidate the stuff in FM:P all that much. The preface of the TC section was written in July 3063, so the info itself may have been collated earlier. Its possible that the events on Texlos occurred in late 3061/early 3062 so the info in FM:P may be relatively fresh as far as its concerned - the Vandaley's feud with the 3rd Taurian Lancers still works, though it wouldn't have been a pressing concern at the time given the Valkyries location in the FWL and not on the TC/FS border.
Chris