Vintage Postcards - postmarks and cancellations

Having had an interested in stamps as a child, and an interest in vintage postcards today, I was unaware that there was such an interest regarding postmarks or cancellations. Again this is a field I am very new to but it's got me more than a little interested. I've found a handful of vintage postcards with squared circle postmarks, which seem to have quite a market.

<- 1905 Birmingham squared circle postmark on a vintage postcard

I've also come across a few duplex postmarks on vintage postcards, the odd cachet, single ring cancellations, postage due cancellations and examination marks. From what I've read up on, there even seem to be subcategories and specialist areas within these categories. I still collect vintage postcard for what's on the front of the card, but the reverse side is now beginning to hold an increased interest for me.

vintage postcard showing a duplex cancellation ->

Feel free to visit my vintage postcard web pages and have a browse around ... and maybe even buy something!