Unless you have done this for many years, you may not know what some pieces look like other then from a book or picture. So here are some tips when buying retired pieces, particularly some of the more expensive pieces. Swarovski has developed and patented a 'clear' component glue. If the glue looks yellowed or foggy, the piece may have been repaired in the past.
Tails can snap off cleanly or even worse, be chipped and ground back to some sort of smoothness.
Unless you know what the piece should look like and feel like, be very careful. This is most troubling with the Lovebirds. If the piece has some frosting on it, check carefully, this is where damage can show up. The snowflake ornaments have a metal tag at the top which identifies the year of the piece. The tag is attached by a crimp through a small hole at the top of the ornament.