The further development of the ward-system in the Roman tumbler-locks, though it certainly existed, is involved in uncertainty, since none of the wards appear to have been preserved, but the fact of some kind of ward having been used is evident from the slits in the keys represented in fig. 122, Plate X., which are of common occurrence. The cross-shaped wards beneath the Indian spring padlock already described in connection with figs. 53C, 54C, and 55C, Plate VI., must certainly be considered to be wards, although open to view, and not concealed beneath the lock-plate. There are also found in association with Roman remains, keys of which fig. 123, Plate X., from Chalons, fig. 124, Plate X., from the Museum at Saumur, and fig. 125, Plate X., from the Museum at Saint Germain, are examples.[37] These keys so greatly resemble the Asiatic keys used with the spring padlock, that it is difficult to believe they were not employed in the same way, but as they also resemble the Roman perforated plates of the tumbler-lock keys that are provided with teeth, it is probable they may have been intended for raising tumblers in some way not yet explained. No tubular spring lock adapted to be opened with a key inserted underneath, and opened with a lateral movement like the Indian and Egyptian ones, has to my knowledge been found amongst Roman remains. Fig. 126, Plate X., is a modern English latch-key of similar form, furnished with a ward-plate and used for raising a common latch: they are now generally disused, from being unsafe. With the revolving keys resembling the modern form, found at Pompeii and elsewhere, slits for fixed wards are common, and show that the Roman keys of the commencement of the present era resembled our own. During the Middle Ages reliance was placed almost entirely on the ward system, and many complicated contrivances were introduced, of which fig. 127, Plate X., is a specimen, until the close of the last century, when their insecurity led to the re-introduction of tumbler-locks. [37] 'La Ferronnerie,' tome ii., Plate LV., E, G, K, p. 238.