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), 54 4G Mk IV (project), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser.