brazing happens at a lower temp. than welding. the brass filler metal melts at a significantly lower temp than the steel being joined. when used to produce a fillet where two surfaces meet at right angles it can look a bit like a proper weld. if you know someone who welds, he can probably tell by looking at it, the photos are a bit hard to tell. brazing is essentially like soldering where the filler melts and wets the joined metals which may be dissimilar to each other as well as the filler.
the much higher temp of an electric arc weld not only melts the filler but the base metal being joined it requires the filler as well as the two parts to be joined to be similar (ie. all 3 steel) and would seriously affect the heat treatment hardening/temper of a blade. the temp. used to braze while lower is also high enough to affect the temper.
i've not heard of tangs being held into iron grips by melted and poured brass, i suspect if anything they would have used lead. cutlers cement (tar or rosin mixed with brick dust and occasionally a fibrous material) was used for similar purposes at even lower temperatures.
this site has info on arc welding, as well as brazing and other welding/brazing methods.
as everything is covered up by the brass, an xray may be the only way to tell what is underneath. the xray will likely cost more that the item did tho. or you could take it and give it a good whack against a tree & see what it looks like when it breaks loose tho this somewhat detracts from it's appearence until you get it unbent and re-brazed anyway
.
modern electric welders like MIG and TIG types can also braze with a brass based filler, again at lower temp.