Hall China started somewhere around 1902 in East Liverpool, Ohio. That area was the main mecca for potter for quite some time. As pottery in the USA became in higher and higher demand, many of the companies moved across the river, to West Virginia. Hall remained behing and expanded in Ohio. They were known for developing the single-firing technique, by eliminating lead in their glazes...therefore becoming far more prevelant in the food-use potteries. Their tea pots are very collectable...and I personally collect their Golden Glo pieces. Keep checking on places like ebay, to get an idea as to what your pieces are worth.
Just an FYI... keep in mind when looking at referance books and price guidelines, of which Hall has many, that current prices are determined by whether the writer has the item and wishes to sell (the price can be inflated) or wants the item to buy (the price can be artificially low). I like to think of the price guide quote as a 'wishful thinking' price.
gessie, the difference between those things is something you learn to recognize after you've handled and looked at enough pieces. If you look up transferware and flow blue and study some pictures, you will begin to see how they appear and how they differ. Better yet, visit an antique store and hold them in your hands and examine the pieces close up.
The flow blue part is a technique where the transfer with the blue is applied and fired, causing the blue to spread or "flow", hence the name ... the floral pattern on your flow blue pitcher is most likely a transfer. I can't imagine it was painted by hand. You can have transfers on pieces of flow blue.
The term Flow Blue itself broadly describes predominantly hard, white-bodied earthenwares decorated with underglazed transfer printed designs. Once applied, these designs were caused to bleed or "flow" into the undecorated portions of the vessel. The addition of lime or chloride of ammonia into the protective shell of the fire-clay sagger surrounding the wares while firing the glaze produced the desired "flowing" effect.