Postmarks Of Colombia: What To Look Out For?

Hi,

I'm interested in postmarks/cancels, but I know very little about the postmarks of Colombia, and what one should look out for (the "keepers"). It's always fun to find a valuable postmark on a common, minimum-value stamp. Makes you want to check everything.

I have no idea what is scarce. Little outposts deep in the jungle? Tiny isolated towns high up in the Andes? I assume they're probably scarce, due to isolation and low population but I don't know how to identify them other than searching for population online and extrapolating from that. I assume some people collect them (who know more about the subject)? Are there certain types of cancels to look out for? It does seem to me that easy to read cancels can be difficult to find from Columbia (and Latin America in general).

Is there a "market" for scarce Colombian postmarks, like there's a market for postmarks from other countries (Australia, for example)?

Some examples:


MEDELLIN(very large population=probably common)
BOGOTA (very Colombia's capital, large population=probably common)
PASTO (Narino department capital, large population=probably common)
...AGENCIA (not sure, maybe a postal agency? if so, possibly could be scarcer, due to not being a full post office?)
JERIC...possibly JERICO? (if so, probably not so common as Medellin/Bogota, but 15000-20000 people in 1950s, so probably not scarce)
large black X (not sure, but looked different, so I included it)