First Day Covers (FDCs) commemorate the first day of issue of a postage stamp.

Summary of things to watch for:

• Cachet - cachetted are better than non cachetted
• Cancels - standard vs special or local. Special may be worth more
• Addressing - unaddressed are better than addressed
• Special - usually worth more
• Topic - popular topics are worth more
• Configuration - blocks etc tend to be worth more if of interest

Cachets are:

• Additional, usually coloured printings on the cover, normally at the left side, and related to the stamp issue.
• Sometimes additional material is glued to the cover, silk (covered pictures which are quite nice usually), silver, gold etc
• Some cachets are very nice and really add to the beauty of the cover.
• The cachet maker usually makes a limited number of covers. Of course some large cachet makers make large numbers, the smaller ones make smaller numbers. The smaller the number of cachets made, the more valuable, relatively the cover will be
• Some cachet makers make one of a kind, hand painted etc, these are worth significantly more than a high volume cachet
• Some folks collect the first issue of a given cachet maker, they do tend to be worth significantly more than other issues

Cancels

• Cancels, especially in the modern era, tend to be consistent, ie the official FDCs often have cancellations from a, or a small number of specific locations
• Some collectors create their own FDCs using local postmarks, with official cachets or their own
• Depending on the collector's preference, either might be more valuable. In my experience, collectors tend to prefer the official cancel and location.

Addressing:

• Originally FDCs tended to be created and mailed to the person who subscribed. This meant that the person's address was on the cover itself, in the usual spot
• Sometimes to speed things up for the cachet maker, addresses were affixed with adhesive labels, which do tend to deteriorate over time. Be careful about FDCs that have been stained by deterioration of the label.
• In the modern collecting era, collectors tend to prefer FDCs which do not have addressing on them. Generally an addressed modern FDC is worth somewhat less than an unaddressed one.
• Older FDCs are very hard to find unaddressed, and most FDC catalogs will identify the age at which one can expect to only find addressed FDCs.
• Note to watch for FDCs that have had addresses erased (often they were done in pencil, especially on older ones) or the stickers removed (you can often see the stain from the glue on the envelope)

Special FDCs:

• Based on the location they were cancelled. In Canada for example some were cancelled with a cancel in the legislature
• Some tourist attractions create FDCs
• Some FDCs are combination FDCs including coins etc

Topics:

• FDCs that reflect a given topic are usually worth more than similar non-topical ones in the same timeframe
• As examples, the first Baseball US FDC is worth more than other FDCs in the same timeframe, as are other sports related FDCs later (like Football and Baseball)
• The more popular the topic, the more likely it will increase the value of the FDC

Configuration:

• Normal FDCs contain the issue itself
• FDCs do come in configurations with plate blocks, blocks coil strips etc. Generally these will be worth more, but desirability depends on collector interest

Notes:

As with all Ebay auctions:

• See how well the seller describes the covers
• Review the feedback of the seller, especially with respect to what they have done in the cases of neutrals or negatives, it will help you see what the seller does in situations when there are issues with their lots!