Cool, Some guide lines from a rookie. Some items will be hard and some easy , to many just downright a lifetime challange. I would first start with the easy ones and get them tagged and valued, then the task will not only seem less daunting but each one you discover the knowledge gained is worth three more. Then the items will be alot based on what they are, i.e. Silverplate short period of popularity and well recorded and marked. Silver had a long history but actually was well marked, because of the value. Then you have porcelain with extreame long history and half the item are unmarked. With that in mind, look to the clues you have and narrow the search.
1. Look at the item from a distance, does it feel old? Kinda weird but on the path of learning this will help in the long run, you will prove and or disprove why you felt that way and soon the first hurdle. Is it Antique, Vintage, or just decorative, This will determine the base of the value for your item.
2. Is it handpainted or decal, my memory is not jogging me now but decals have been around for awhile early 1800??? (help me guys)
but hand painted can mean older, but not alway so. However it will make the value a bit more, Nothing like having a item that was personnaly in the hands of a Artist, not just done decal applied before glazing.
3. Try and grab at the Period. i.e. victorian, Art Novea and etc. This can be difficult since many items have been redone with the same molds or just the style came back in vogue over the year, but if you can grasp at the first question of Antique vs. Vintage you will have come a long way.
4. Markings, they may seem the most important sometime but they should be the ice on the cake (MMM mush cake)
, (Sorry bad spelling and bad humor). I have invested in several cheap books to browse through and the internet is wonderful too, but the first three should be asked first just to lock the knowledge in sort of speak.
5. Then if that fail and no ground is made you have D.B., K.C., Rall.... (don't remember how to spell)., Cogar and all the rest . Lol
Anyway back to the plates. Are they hand Painted? and can't make out the markings? The base value of plates can easily be established by a price between Replacement and searching Ebay? Look to items that is only getting bid and make you list ending soonest. I've written so much blah, blah I've forgotton what they looked like. Excuse me as I go back and take another look before I sound like a Jr. that I am.