[dorkfish]

From what I have read in the past...L.F. simply means low altitude variant. This was different RR engine.. (and maybe other things?) But there are L.F.s that do have rounded wings. So the L.F. does not mean clipped wing variant.

Edit to add a backup source: They seem reliable.

The Mk V saw the first appearance of the F (fighter) and LF (Low level Fighter) designations. LF Mk Vs used modified Merlin 45M, 50M and 55M engines that produced their best power at lower altitudes. With the appearance of the LF Mk V, the standard Mk V became the F. Mk V. The LF Mk V could reach 355 mph at 5,900 feet, making it as quick as the Fw 190 and faster than the Bf 109G. The Mk V also saw the introduction of drop tanks to carry extra fuel, initially a 30 gallon model and later a 80 gallon version. It was also the first Spitfire to be adapted to carry bombs.

http://www.historyofwar.org/articles/we ... e_mkV.html