Paul Bender's post on F-units permitted in passenger service triggered a thought that first came about while indexing the FMIG Newsletters: when did the FP-7 units receive the second "Mars" headlight, and when were the fuel tank skirtings removed? Some references and dates: Ken Wulfert's "Enid" collections shows post-renumbering #41 (ex-5041) and #50 (ex-5050) both with Mars lights (dual headlights) and sans skirting. FMIG Newsletter #17 (August 1978) has two photos with information. In that issue, Glenn Young inquired: "Does anyone haev a slide/negative of an FP7 without "Mars lights?" Doug Hughes replied: "My guess is that they were delivered without Mars lights and they were added later." Photos in NL #17: #5045 at Springfield, 1951 (Arthur Johnson) - single headlight #5047 at Springfield, 1951 (H. Vollrath) - single headlight FMIG Newsletter #19 (February 1979) shows a photo of #50 (ex-5050) at Springhill, KS, 1969 (H. Vollrath) - Dual headlights and side skirst removed Other photos I've seen: #5042, Unk Date/Location and photographer: Full skirt and single-headlight #5047, Ft. Smith, 1964, M. Condren, Dual headlights with side skirts removed. Thoughts?