Refer to prior article on Fractured Bridge Pipes. Knowing the approximate time of introduction of the plastic sleeve on the bridge pipe leads to some interesting logic. Jaguar notes introduction of the Dunlop safety tag (sleeve) in July 1958. Dunlop would have put the sleeves on all brakes, MG, Jaguar, Ferrari etc. from July 1958. Twin Cams were in production starting April 1958, although they did not officially go on sale until July. Early Twin Cams did not have the sleeve on the bridge pipes. Some subtle clues such as the master cylinder mounting box change, and the number of Deluxe cars built indicate that the Dunlop items (brakes parts and wheels) were bought in batches of 500 parts. It would follow that the first 500 sets would not have the sleeve, running from first car number 501 to something close to car number 1000. Apparently the change was made a little earlier, as the bridge pipe length was changed for the front calipers at car number 836. A bit of speculation might mean the other 165 sets may have gone into the distribution chain as dealer spare parts (or the original bridge pipes may have been thrown out for safety reasons).

So assume that the first 426 cars did not have the sleeve, and all cars to follow did have it. The part without the sleeve was superceded by the part with the sleeve with no change of part number, and all following replacement parts would have the sleeve. Then for concours the early cars could be shown with or without the sleeve on the bridge pipes, depending on whether the pipes were ever replaced. These early cars should not be penalized for presence of the sleeve as it is a safety item. Beginning with car number 836 the front calipers would have the sleeve, and the rear calipers also about the same time but not necessarily exactly at the same car number. Another observation is that current replacement parts may not have the sleeve, so the concours enthusiasts may want to work on the parts suppliers for that little detail.

The "P" clip was apparently never incorporated by Dunlop. MGA Twin Cams prepared by the MG Competitions Department had bridge failures in 1959 and 1960. The Twin Cam went out of production in 1960. On 20 Dec 2006 Mick Anderson reports, "I have done a lot of work on Jaguars and they never had the "P" clip, even years later. I am presently overhauling a set of Dunlop brakes off an 1968 Jaguar E Type and it does not have the clips (does have the sleeves)." Today it is common practice to install the p-clip on all Dunlop calipers, at least for all competition cars and recommended for street cars as well. As this is done for safety reasons, it should be accepted for concours with no penalty for originality.