puyuan wrote:
If the only major difference is the factory I highly doubt anyone would... Though sometimes different "zi" clays used to give me different results in my water tests (mineral water first, distilled second; 15 minutes each pot and 1 zisha kettle). I was afraid my kettle would be redundant with some of these pots, but luckily it was always distinct enough. I think it was lower fired than any of those, though.
it can be possible to tell the difference if the pot is lower fired, or if its used to boil water (contact with water is much longer than steeping durations for tea).
but when the pot becomes higher fired, more glassy like, the tendency of it to have a clay scent (caused by leaching ions), is lesser, and the catalytic property of the clay also decreases, so it becomes more "glass like", so the tendency to affect the brew also decreases.
with continued usage, the surface porosity of the pot becomes blocked by tea stains, the outside becomes glossy, the inside becomes rather stained, that also further reduces the "effect" of the clay on the brew, and now you have a vessel that is "mature", possibly neutral to the brew. i had the fortune of receiving a couple of well seasoned/used pots and was able to compare the brewing to a similar pot of size,shape,material,firing of the same era.
not discounting the fact that it indeed can be possible for someone to discern and identify the taste of a brew from a particular pot if he has spent enough time with it. but without seeing the pot, nor having used it before, to be able the tell the clay type, era, factory type is just miraculously
as the properties of the pots are right they can be used interchangeably, regardless of which factory, or whether its not factory made either 
