the engraving here of henry v shows a lot of similarities of period styling. The knee and elbow armour the thigh segmented armour, the martingale bit, the breast collar design,
Notice the way the horses head is held high and back. This is very distinctive of that period . The horses were even bred to have thick necks like that.
http://www.britishmuseum.org/research/search_the_collection_database/search_object_image.aspxMy feeling is that it cannot be 19th or 20th century because nothing was cast so crudely in the industrial revolution period . Victorian iron and steel engineering was superbly crafted and the Victorians were very exacting about quality and finish.
The figure has very fine detail but is a simple crude pouring cast as apposed to the lost-wax method which would give a figure in-the -round rather than bas relief. The finish is polished and has a deep patinia just as bronze might have.
Plus I wouldn't expect bronze to be used more likely lead or pewter or some alloy mix even copper or tin but not bronze.
I agree about 99% of common folk never seeing much of what goes on in the cities in the Plantagenet /Tudor period . There were many paintings ,engravings, books etc but again only the educated would have access to them but whoever sculpted this figure originally would need pictorial material in order to sculpt in such detail. Presumably it must have been available even back then