Hi Walt,I took a long hard look at that pic - Wow! What an interesting picture.
It does indeed seem to be a actual picture from time and place, I just don't know how to interpret some of what I am seeing. As a for instance, looking at the leggings themselves, I find it hart to tell from the picture wheter they completely encase the leg, or whether they cover the front only - sort of a pair of 'arming hose' with attatched mail.
I am dubious about the area around the crotch, how it seems to just be an extension of the legs. I would think what the artist may have been trying to interpret was a pair of mail arming shorts worn in conjuction with the legs.
The bevor is very interesting too - The photo I have seen of one is quite bevor shaped, and for it to have worked , it would obviously have to have been sewn to a padded foundation chin guard - that is probably what is going on here.
The armour lookes very Italianite in construction (that is the most compact tailed visored sallet I have ever seen depicted - I don't think I've seen a surviving one quite so compact. The plate could also be South German.
You might find what I am saying a little confusing - it is very 'gothic' looking, but you will note there is no indication of points on the couters, and no belt round the front of the cuirasse, so it seems to me if it is a detailed depiction, the artist is showing armour that is put together in the Italian export facshion, but obviously decorated for a German clientel.
I think the artist may well have been unfamiliar with some of the nitty-gritty details of what he was looking at, but has depicted the subject true to what he was seeing. The cuirasse is for mounted service, as it has the lance rest.
I think what we nay be looking at is a normal harness that has bits left off specificaly for foot combat. If the mail is very fine, and it only covers the front of the leg, perhaps it allows a greater freedom of movement. I know the mail 'bevor' probably does. I would have doubted that article except I have seen a photo of one.
The fellow though from the detail of the plate harness is most likely a man at arms, wearing his harness with these funky adaptions for foot combat. It can't have been a wildly popular rig, as this is the first time I've seen this sort of getup in art of the period in question.
I haven't heard of that particular book. To give fair warning, facsimilie prints from the 19th and early 20th centuries (thats when the intrest in things Medieval was in full bloom amongst the wealthy members of European and American society) tend to be very expensive. From multiple hundreds to multiple thousands of dollars.
Hope this helps. Hopefully we can get others commentary on this. 
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Bob R.