Dating victorian bottles
Simply knowing when your perfume first came out can be a huge help.
Please remember that some perfumes were made for many years after their launch dates, on the other hand, some perfumes were only sold for a very short time.
Look on the base of your bottle for acid stamps for Baccarat, Lalique, Cristal Nancy or Cristal Romesnil, these markings add value to your bottle. Only from 1936, Baccarat bottles were systematically engraved with a mark.
Art Nouveau is generally 1900-1920s, Art Deco mid 1920s and some styles carried into the 1940s, psychedelic late 1960s-early 1970s. You might encounter labels which have the date stamped on the back of the labels.
Sample bottles from the 1950s onward, often had labels that would say "sample, not to be sold". Factice, or display bottles, were not meant for resale, and will have labels such as: "dummy, not for sale".
Later, many bottles often have their batch codes engraved into the glass; (Chanel, Dior, Thierry Mugler, etc).
The styles of the boxes or labels can also help determine age. Some labels can be read from both sides, looking thru the back of the bottle.