I have heard that kind of thing before about speedo faces. Curious really, as I routinely clean PA faces and odometer dials with T-Cut and don't have problems as a result. I have probably averaged a PA speedo a month treated in this way for the past 20 years or so. I can only conclude that PA speedo dials are made of stronger stuff that Chronometric ones.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser.