How Do You Recognise Real Unperforated Stamp?

Hello
I often run into stamps that have one or two sides unperforated, and I'm not sure if it was ment to be that way, or was trimmed for some reason.
How can you know?
When did this one/two side unperforation start? Was it due to introducing coils?
I'd like to hear your input on this. Thanks

Coils are supposed to be imperforated on two opposite sides, generally. Some stamps are imperf on one or two sides but are not coils, that is because they are from the edge of a sheet that does not have selvedge. In the examples you show above several of the stamps seem to be cut by scissors for some reason.
Some stamps that are imperf on just one side may also come from booklets.


Peter

It is very difficult to tell a real coil or imperf stamp. They are very expensive compared to the perf'ed stamp, so if you must collect them, ( Canada and USA collections are NOT complete without them. ) you have to be very careful. I collect pairs because it's very difficult to fake a pair. For example a Canada #109 is $30.00 VFH, a Coil, #130 VFH is $100.00. A very good reason to trim the sides of a perf'ed stamp! It is easier to catch if you have a pair. I wish I didn't have to collect them but they are in my album and that hole must be filled!

Thank you both. So, is there a way to know? When did stamps start to be sold in sheets where the side wasn't perforated?
My main problem is with older stamps, where size isn't always the same.

There is no sure fire way of knowing without a certificate. My buddy uses a special microscope, he says you can see the knife marks. Buy from a qualified stamp dealer and be careful. If you buy expensive coils or imperfs online, make sure you can return them. I return about 50% of the coils I buy on E-Bay!

The French and German stamps you show simply appear to be cut by scissors, either when being roughly separated from a sheet (eg in a busy office) or removed from a cover. The GB stamps look like booklet stamps. GB coil stamps were perforated on all four sides, as far as I recall.

Rob Roy, do you have a Scott catalog? There is an explanation how large sheets of stamps were cut in four smaller panes, leaving two edges of those four panes imperforated. The same explanation is on several posts in this forum.
Coils are a different problem altogether. One of the ways to make (relatively) sure they are OK is to collect them in pairs. That is not always a 100% guarantee, but it helps.


Peter

Thank you for the profound answer of my questions.
I buy cheap packages of stamps, or kiloware, and later plan to trade one-on-one.
Currently I haven't any catalogs. Did anyone try the free aplets of Scott for Android?
I bring questions to this forum when I can't solve it by myself, or when it has a general knowledge issue, like since when there are side selective perforations on stamps.
Hope it's ok.

As others have said, it's best to buy these things in pairs: it's much harder to fake a pair.

This Hyderabad State 2 Anna stamp probably began life as an imperforate between pair, which some idiot cut apart with scissors



Of course if you like that sort of thing, Travancore-Cochin State is a happy hunting-ground for them, and - relatively - cheap, like this block of four



(SG 011cd, for those who follow such things)