Firstly, I must state that I am not an error note collector. I find that error note collecting is a very specialized area to the point that error collectors are almost another species. In fact, I find that the value of error notes is not only related to the type of error and the condition, but also to provenance. Literally, the same note in the hands of different people is worth different amounts depending on who owns it. And this bit of information tells us that error collecting has a great deal of scepticism involved.
Much of the scepticism has to do with how notes are being offered in the present digital age. Buying notes online means not being able to inspect the product first-hand. Being able to authenticate an error note is of the utmost importance to a prospective buyer. It's even more important than being able to ascertain the grade or the originality. At least from pictures, you can get a feeling for a note's state of preservation, and even if you make a mistake and buy a note that has been cleaned/pressed/trimmed/restored/etc., your note still has a tangible value associated with it. By comparison, if you buy an error note that shows signs that it may have been created secondhand, your investment is lost completely.
There are several error types that can be faked, and they are still legitimately collectable. Missing serial numbers and missing holograms are two such types. To buy such an error note, one has to be careful and intelligent. There are many more fake errors than legitimate errors in the marketplace. All the notes with missing serial numbers I have seen have been low grade. Consequently, a genuine error note should be sought in high grade, preferably Uncirculated. Removing 100% of the ink from a serial number is nearly impossible to do without using physical means, and the damage caused by rubbing the area of the note where the serial number is printed can be easily disguised on a well-circulated note.
Undersize notes are of no value to anyone, even with the claim of being pulled from a brick. It is just too easy to trim notes. Ever heard of X-Acto knives? Anyone with a thin, sharp blade and a straight edge can trim a note. Only a real pro can decide if a note is worth trimming and actually fit the trim job to the note, meaning they can remove most clues that could make someone suspect a note has been trimmed. You know, clues like perfect 90-degree corners on a VG note, and fresh edges on a dirty/stained note.
Getting back to the subject of provenance, it helps the value of your collection if you have a good reputation. If you are a well-known error collector, or even if you are a brick hunter, you have something that tells people your opinions can be trusted more than the average eBay seller. People regard bricks as virgin notes, that is, notes that have not been handled by anyone since being released from the factory. Once a note hits circulation, anything that happens to that note cannot be called an error, and it becomes exponentially more difficult to diagnose a fake error from a legitimate error that evaded quality control and slipped into circulation.
The only thing your mind fails to comprehend is that is simply takes time to build a reputation in the collecting community, especially if you're focused on error notes. Those intangible people skills are that much more important if you plan to buy and sell error notes compared to any other specialized area. In fact, all you need to be a specialist in radar notes is a pulse. You can be blind, deaf and dumb, and as long as you (or your caretaker) send your notes to BCS or PMG for grading, you can make plenty of business while being completely inert.
