Be alert to bogus postmarks on North Vietnamese military covers. This post illustrates two examples with different levels of sophistication.
I obtained these covers at different times from a trading partner in Hanoi, whom I don't think realized that these were bogus. We exchanged want lists and acquired items for each other. I am convinced that these and other covers were custom made for me from a faker in North Vietnam.
In other words, my trading partner asked a stamp dealer for a particular stamp on cover and was told to check back in a couple of weeks at which point, lo and behold, the seller had come up with the stamp on cover. These particular stamps are not at all easy to locate used on cover, however they are readily available in mint condition. The seller could remove the stamp from a genuine cover or create one from scratch.
The first cover is a simple fake featuring the orange military stamp depicting a soldier with outstretched rifle. It is meant to be an adversity envelope made from a piece of notebook paper due to the lack of paper during the war. In reality, the paper is clean and nice smelling(!) so definitely not genuine. More obvious is the cancel, which looks to be hand drawn with a pen. It is not quite round and you can see the individual pen strokes.
The second cover is "better" in that the faker went to the trouble of soaking the original stamp and postmark off the cover. Unfortunately, he got a bit zealous with the water, leaving water stains and smearing the ink in the address. But we've all seen Vietnamese military covers in much worse condition, so this is not an immediate tip off.
The benefit of this approach is the faker has genuine postmarks on the reverse to lend credence to the cover
The postmarks on the front of the cover were then applied, again apparently drawn with a pen. At least the forger knew enough to make these an earlier date from the receiving marks on the back. But how many NVN military covers apply an additional cancel to the decorative cachet?
I have a dozen or so examples of fake covers like these, so let me know if you are interested in seeing more (and yes, my trading partner provided enough genuine material to make it worthwhile maintaining the relationship).
Some of the fakes have hand-stamped postmarks making them more difficult to identify, and some appear to have been made by another person with a different "style", but all have the same pleasant smell (Vietnamese military covers don't smell nice!) and all have a random splash of something on them that glows brightly under black light that leads me to conclude that they all came from the same source.