Why pay an expert committee a minimum of $30/$35 if your stamp is not what you thought it was?
Hello and welcome to Weiss Expertizing service. I offer preliminary expertizing of any United States stamp, cover, essay, proof or cancellation for only a small $10.00 fee or $15 for my Certificate opinion.Click here for more information. As a general rule, any 19th Century unused stamp valued at over $100 by Scott should be certified. As an examiner for two expert committees, I would guess that 80% of the 19th C. "unused" stamps I see are either cleaned (with cancels lightened or removed) or are regummed or both. Any used stamp where the Scott value is substantially higher used than unused, such as Scott #30, #39, etc. should be expertized. Any stamp which can easily be made "imperf" by trimming off perforations and by doing so, increase the value greatly. Check out the two different service options - the $10 opinion on an enlarged photocopy or the $15 opinion on a safety-paper certificate. Click here for more information.
Why have your stamps expertized?
The reason for expert certification is simple; it is to have an independent third party confirm and insure that the stamps you buy are genuine and "as described". Expert committees indentify stamps and describe any flaws, repairs or alterations that deviate from a "perfect" stamp. It therefore is important for buyers to avail themselves of the expertization process to protect themselves from possible financial losses they may suffer due to misidentified or misdescribed stamps or those with undisclosed faults. One way to think about it is as an "insurance policy" against these types of problems.
All mainstream philatelic public auction firms, and most top retail dealers allow buyers to place purchases "on extension" for certification. Unfortunately, not all sellers on eBay allow certification. Therefore, to buy expensive stamps from such sellers is a big gamble. I strongly recommend the Guide written by "philcomp" "Buying Higher Value U.S. Stamps on eBay," for excellent general guidelines.
the 19th C. "unused" stamps I see are either cleaned (with cancels lightened or removed) or are regummed or both. Any used stamp where the Scott value is substantially higher used than unused, such as Scott #30, #39, etc. should be expertized. Any stamp which can easily be made "imperf" by trimming off perforations and by doing so, increase the value greatly. Check out the two different service options - the $10 opinion on an enlarged photocopy or the $15 opinion on a safety-paper certificate. 
protect themselves from possible financial losses they may suffer due to misidentified or misdescribed stamps or those with undisclosed faults. One way to think about it is as an "insurance policy" against these types of problems.