Bottom line is:- Having material another collector wants in a listing to his understanding YOU design. (Maybe this is something Peter is thinking of doing!?) That means YOU make a list of YOUR available exchange material to SG, Scott, Michel, SACC to MNH, Mint, Used etc. on .xl. Sounds like a lot of work, yes - well YOU want to exchange and to avoid exchange disasters be clear in what you have and be fair in your transactions and you will only have little problems. Like the old story - when you want something work for it.
One snag about building your own is the ever possibility that your system crashes so you would have to bear that in mind. Even with new technology araound every corner you would need to back up and keep your data alive.
Have you found a site that provides you all in your list? Maybe creating your own page/site could be a good thing for this.
Zararina, it is a little bit of a mixed bag as both sites only give some of the functionality that I was looking for. I think the below would summarize it: Mark my collection against a pre defined list. (Colnect and Catawiki) Note the condition, album etc. (Colnect and Catawiki) Mark items I want on a wish list. (Colnect and Catawiki) Auto match the wish list against other members for exchange. (Colnect - but at a price) Export above lists (Colnect and Catawiki) App to take the collection offline on iPad (Catawiki - but only in Dutch) I believe both services looks pretty good. I used Catawiki to add about 150 items to a collection to check stability and service. Very easy too use with good images.
