The former British Colony of British Guiana has some of the most valuable stamps ever issued. The World Famous One-cent Magenta from 1856 is considered the world’s rarest stamp, valued in the millions of dollars: well beyond the reach of most collectors, even if you have the money. I believe this is one of the few stamps not owned by the Royal Philatelic Collection in Britain.
But that does not mean that there are no affordable varieties to be had by most collectors who have the patience and knowledge of what to be on the look out for.
These two stamps shown below were both issued in 1907. One is worth about double the other. Can you see the difference.

At first glance, they are strikingly similar. But there is a distinct difference. Can you see it?

British Guiana Sc# 172 (Type I) & 172b (Type II)

The difference is in the Flag & the way it hangs from the mast. In type I, the flag appears to be attached to the Top of the mast while Type II, the flag is attached to the mast along it’s complete vertical edge

British Guiana Sc# 172 & 172b

Browse collections & online sites carefully and you can find these varieties. The difference in value is not huge, but they are easily affordable varieties to add to your colelction.
The devil’s in the details
Happy hunting.