Want: Cities, Towns In Postmarks/Offer: Dates In Postmarks

I collect worldwide readable cities/towns/places of cancel in postmarks on stamps. I have traded a lot with people who are looking for readable dates in postmarks, since I haven't found anyone else who's collecting towns as I am. Therefore have a lot of dates to offer in exchange for towns.
I like to keep it simple by exchanging batches of stamps. I do not do any trading based on catalog values.
Below is what I think of as The Holy Grail. But postmarks on pairs or next to stamps are OK with me as are partial but surely identifiable names.