Hello Elefterka, and welcome to the forum.
Ah, a chance to ramble on late at night! Thank you!
If there are any stamps amongst your stuff in the attic then all the folks here will be happy to help to figure it out. Scans or photos help a lot.
If there are no stamps then I suggest looking around on the internet, on
ebay and any other area that has lots of stuff listed for sale.
Or just take some (not all) to an antique store and see what they will give you for it. I found that antique dealers (and other dealers, stamps included) have to give you a small fraction of the their selling value of things because they have to turn around and sell it again and pay their overhead etc and make a profit.
It takes some time to acquaint one's self with anything and find the people that know stuff and the people who will pay for stuff. And sometimes people will know some of the info but not all and unintentionally mislead you on your search.
Unless you know about something, stamps, ceramics, anything, it is hard to determine the value of it and the value is always dependent on who wants to buy it and how badly they want it too. Even if you list it piece by piece on
ebay or some such venue, the chances are that you will not know enough to describe it correctly and know whether you are getting a realistic (not fair, just realistic) price for that item.
On this forum you will find many lifetimes worth of knowledge about different stamps, but surprisingly, everybody is always learning something knew all the time. There is that much to know.
Like, for instance, if you have an old iron bed headboard and foot-board (if such a thing exists) then maybe you will find someone who knows where to sell that for the best price, assuming you are a good salesman and people person too. Otherwise, that one person you found might tell you, well, go to Joe's, he knows about this stuff, but Joe doesn't really know, he just has heard Hank talk about it a lot and will probably call Hank or just buy it from you and sell it to Hank, who will sell it on down the road to someone who really wants it and can appreciate it because it is just like the one in Washington's house that they saw last year, etc, etc.
I ramble on. The point is, some things do not have an intrinsic value like money or coins. Stamps do not. Antiques do not. people's perception of their value to them make them worth something. That is all. Like diamonds. Don't get me started!
if you are historically minded then maybe some of your stuff will be of interest to keep and research further at the library or
ebay or elsewhere. I would do
ebay but that takes work and effort to get right also.Good for research sometimes.