I don't know if these still exist, but photos do. These were at the Bayerisches Nationalmuseum in Munich. You can click on the images for a magnified view.
Inside of the legs. Note how the lower leg laces on the inside for a snug fit over the ankles.
Outside of the legs.
These resemble those worn by a 1490 St. Michael by Juan de la Abadia.
Also see the legs of the soldiers in the arrest of Christ from the Petites Heures of Jean de Berry, in that case worn with plate knees. A soldier bringing Christ before Caiaphas showes similar protection on his thighs.
And similar legs are shown on an emperor in the illumination in this thread, again with plate knees.
I originally read the Munich hose as hose to wear under plate legharness, but I no longer think that’s the case: instead I think they’re actually intended to serve as leg armor themselves.
The mail patches were not located at the back of the knee, where they would cover an inevitable gap in plate legharness, but with two strips of mail on each side and two in front of the knee. All but one of the strips in front are missing, but spotting, the remains of stitching, and the location of the remaining strip in front shows where they were sewn.
The illumination of an emperor shows him going into battle in similar hose, not preparing to arm.
I think the Munich hose was made of non-overlapping metal plates sewn between two layers of fabric, similar in general principal to the kikko used in Japanese armor. The brickwork-like pattern, like the hexagonal shape of the kikko plates, would mean that the gaps between the plates would not present a continuous straight line vulnerable to a horizontal slash.
The spotting of the Munich panzerhose inside and out is highly suggestive of rust from plates bleeding through the fabric.
If I’m correct, this would have been a defense somewhat vulnerable to a thrust because the plates did not overlap, but less bulky than overlapping brigandine and perhaps offering superior protection to mail against edge blows.
It would not have been flexible enough to bend easily at the knee, which would need either mail protection, as on the Munich panzerhose or the Abadia St. Michael, or plate poleyns as shown on the other illuminations above
We do know that hose with mail gussets or voyders was worn under plate harness in the 15th century.
I would have thought that patches of mail sewn down to fabric to cover areas uncovered by plate were a 15th century innovation. But look at these images from Lancelot du Lac ((BN Francais 343) 1380-85
I read these as showing most of the thigh protected by plate, with a narrow portion of the inner thigh showing only fabric beneath cuisse straps. Behind the knee itself, however, there seems to be a patch of mail. Look at these, and tell me what you think they show.
f. 13v Note how his helm hangs from a strap attached to the back of his body armor.
There's some interesting documentary evidence in this thread.
There were other ways to protect legs. Walter von Hohenklengin wore plate harness on his legs, and no mail to cover the gaps.
Sir Guy de Bryan (1391) wore full length mail chausses beneath broad plate splints. The splints on the effigy were probably originally connected by applied straps: there were iron pegs at the appropriate locations (six per splint). There is a similar row of holes for an applied upper arm defense.
The St. George from the Champmol Altarpiece, ca. 1390, has mail protecting his inner thigh, but the row of rivets on the adjacent edge of the cuisse and the lack of a cuisse strap suggest that the mail may have been attached to the cuisse.