Davy.
Your watch is definitely Swiss and it is most likely 18 karat gold (although some Swiss watches are known to overstate the gold content). The "K18" is the continental (particularly German and Russian) manner of denoting the gold content. The crown that you mention is likely the German hallmark for solid gold.
Your movement is a cylinder escapement, and appears to be a product of the maker Adolf Schild, although there were several other makers producing similar designs. It appears to be an 8 jewel movement, which would be upper middle in quality, functionally equivalent to a 15 jewel lever escapement watch. These were much more common in continental European use than in the UK or the US. They also stayed in vogue a bit longer, so although I believe Jim is correct in his date range for your watch, it could be as late as 1910 or so.
Cylinder escapements were among the first successfully mass produced movements, and were considered to make up in durability the little that they gave up in accuracy. They were surpassed in quality by the lever movements, and once the mass-production of levers became more common, cylinders were relegated to the second-tier. They would be largely considered obsolete by the 1920s, and few modern watchmakers are versed in their repair. There is also a distinct shortage of spares available, so repair is often problematic and expensive. Since you report that yours is running, consider that a plus, although you should have it checked by a watchmaker when you find someone to replace the bow.
As an heirloom, this is quite a nice watch, and you should be proud to carry it. As a collectible, cylinders are not as highly sought as some other designs, so much of the value will be in the gold value of the case.
