Details, details details . Start with the basics and write everything down. Word of mouth, doesn't always mean a lot. We all make mistakes. Great Aunt Sally might think she has had something for years and years, but you and I both know the old dear's memory isn't what it used to be.
Collectors have specific criteria for the things they collect.
Someone who collects outdoor enamel advertising signs may be forgiving of small flaws, a beanie baby collector won't. There are different grades of almost everything. Yours probably isn't one of these. Use an eyeglass to be sure and record exactly what you see - manufacturers change their marks and different companies often have similar marks. Now that you have looked that glass candlestick over and found the Tiffany signature on the base, the granny must give you the bad news.