Another reason these are very sought after is the fact that over the years many have had the arms broken. Inspect the arms close to see if any repair or cracks are present, this will affect the value. Then also for clue to age consider looking at the amount of tarnish that has developed, these are very hard to clean espically in the arm pits, If they were well cared for which can be apparent in the patina when it is polish and still has very black tarnish in the hard to clean area, you may have a item that is older, but this is just clues to look for. Style is another important factor. There have been some very noticable changes in style, keep in mind that many victorian styles was reproduced in the 30's to the 50's.