Lustre-ware was without doubt the most affordable form of decoration on all manner of crockery throughout most of the 19th century. Therefore there's a lot of it about and not too much of it marked. So....how do you tell who made what and when?
Start with the basics. Work on the premise that whatever you find will post-date circa 1805 (think yourself exrtremely lucky if you find an earlier piece) and pre-date roughly 1890ish when it became finally unfashionable. This is a decent rule of thumb though of course there are exceptions to the rule.
If you find a really nice, bright and shiny example of, for example, a cup and saucer, don't dismiss as modern. If it is modern, it will be marked, possibly by Wegewood or Allertons or some small studio which still turns out occasional pieces - and is still likely worth collecting. Not too many fakes around simply because there are still lot's of bread and butter pieces around which don;t cost that much - and the higher value pieces, such as "genuine" Sunderland Lustre Jugs and Bowls are pretty hard to fake, even though commanding higher prices. And the thing about "sunderland" or more accurately "pink" lustre is that it does tend to stay bright - that's why so much was made!
The fun bit in collecting this lustreware is that not too many factories marked their ware or at least not much of it - but, with a little practice, it's possible to identify the factories very well. Besides which, it remains relatively affordable, particularly if you're a cup/saucer collector. Great fun, for example, to buy up odd pieces for just a few pounds (sometimes pennies), set aside and wait to find another piece in the same pattern just as cheaply. Marry the two or three up and your investment is rewarded by appropriate multiplication at point of sale or swap. Besides which there are still bargains to be had and once your expertise improves, as it will, you will learn to recognise the good buys from the bad.
The bad buys? Rubbed lustre is common as is discolouration of the porcelain or pottery blanks. If the former is not too bad, still worth buying (particularly if you become hooked on collecting different patterns) and if discoloured, still worth considering. For example, discolouration of certain types of pottery is a good indicator of genuine Sunderland, Newcastle or Seaham Factories, all of which can command higher prices.
More on this subject later. For now, this to get something going on the subject in e-bay.