AJB,
Just a few comments about my K&M cases (I am an interested party remember....
)
I have been carrying and using some of my K&M cases for over 15 years. I have never had one fail to keep my matches dry. Early versions had compass problems though. I generally do keep my plastic cap over the compass but none of my early versions came with this cover and for the most part these are doing fine except for some bubbles.
Silva markets a screwtop version using much of the same format as the K&M but only has one o-ring. Keith found that brass and aluminum are too prone to galling with a screwtop seal so decided on the press-fit stopper with tension cord as the best all around method.
If you lube the o-rings too much the stopper can pop out if you do not use the tension cords to hold it in place. I am so used to twisting these open and closed that I find I do it without any thought at all.
The compass Keith currently is using is the standard Suunto compass found in the wrist watch attachment version Suunto sells. I cannot remember exactly what they call this but that little button compass can be removed from the housing and used in the cases if you ever have a reason to do so.
My oldest matchcase is a chrome plated EverDry that one belonged to my Grandfather. It has a twist seal top and is a bugger to open....I still like it though as it reminds me of some of the things we used to do together.