How do you verify season of twiggy, etc?

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I looked on atelier.naff but didn't see an answer to this: How do you verify season on the twiggy and other styles that don't have the silver plate? I have decided a twiggy will be my next purchase.
 
I use everything else in the criteria:
Color
Leather quality
Hardware on bales and corners
The serial numbers on the back of the tag
The way the tag is sewn in
Dimension/proportion -- this is really important

For all of the bags without silver tags, I look really carefully at the dimensions and corners and compare them to the Motorcycle Reference guide. Sometimes a bag will look really good but the dimensions are off slightly -- and when they are the angles of the corner hardware start to reflect that. For example, instead of being at 45 degrees they're at 60 degrees. So if the corner leather detail/hardware is pointing at a different angle to the example on ateliernaff, I know it's a fake. I've spotted about 10 fakes this way that otherwise looked great.
 
flipflop, if it doesn't come with its production card, it can be hard to determine what season it's from because you really only have the color to go on. If it's black, it's totally guesswork depending on the quality of the leather. Some of the blues can be hard to differentiate, too.