Sewing machine roulettes on Vietnamese stamps
Sewing machine roulette (also known as “Perce en points” or pin roulette) is one of the oldest and widely spread methods to separate stamps. As the name suggests, roulette is created with sewing (or similar) machine. In this roulette, small holes are pricked trough the paper one at a time,and no paper is removed (which is why this is a roulette, and not a perforation). These characteristic makes it somewhat easy to differentiate pin roulette from normal perforation. Lots of countries have used it up to very recent times, but as I’ve got my Vietnamese collection open, let’s display some of them.
First a Vietnamese stamp commemorating a centenary of Einstein’s birth. This is a very ordinary pin roulette as the teeth holes have lots of remainders still intact and the result is very uneven.

1979 Vietnam - A centenary from birth of Albert Einstein
Then another item, and something I hope more knowledgeable readers of the blog might be able to answer…. Notice how the following stamps have varying papers and perforation / roulette styles. I’d like to know why such a variance?

1979 Vietnam - Five Year Plan (1976-1980).
The non-specialized catalogs I have, don’t mention nothing about this. However, I know that in some countries (like North Korea) printing quality has been occasionally tied to audience. Stamps going to local markets were printed to low quality pulp paper (and using other low quality methods such as pin roulette) while exported stamps (to western collectors) had premium paper (and other better grade solutions). Is it the same with these Vietnamese stamps, or is this just normal printers variation?
Thanks for this post Keijo, it was helpful. I am also seeing variations in perforations and roulette styles within sets in some older South American issues. Since most catalogues do not list these variations for countries of lower collector’s interest (especially Vietnam) I have not been careful to look for them. I will be inspecting stamps a bit more carefully in the future.
Thanks David
Especially early Mexican stamps should provide lots of similar variation to these.