I've got two of this Casio
model, the one above is the most common model, the second one is the
gold tone model. It's a very cheap, but riliable watch. In my country it
can be obtained for about €20.-, but I have bought these in East Asia
for much less shipped to the Netherlands. They have been sold by
millions all over the world, and I have seen this watch worn by quiet a
lot of people. Although it's a very good watch for the money (it's
pretty rough build too), it's also a bit an infamous model. The use of
this watch is also linked to terrorist activities.
You can read more about this on this page of
a DW-6900, the F-91W looks very tiny and thin.