Watch modification (aside from switching out straps) is work done only by skilled professionals. This is one of the reasons it fascinates me so much. A lot of the modification work done there is pretty straight forward; swapping out hands, changing colors, switching the dial. Regardless, I am personally utterly in capable of doing any of it. For this reason I love the idea, though am afraid to do it to my personal collection. For that reason investing in an already modified watch can be a good idea. You can get a truly unique timepiece, often with appealing traits.
Take this example which is available on eBay right now for about $200. An automatic Seiko SKX013 is modded to look like a MKII watch. Watch modifications that resemble MKII watches are common, and for good reason. Though this is a particularly subtle and inexpensive example, which is good.
Aside from putting on a traditional canvas strap, this watch has had a lot of work. The hands are now "Yao" hands, which make for highly readable (and luminant) viewing, the dial has been switched, and now even has an MKII logo on it, and the date and day discs have been switched as well. The bezel remains original, which looks just fine for the watch. Notice the before and after images.
This watch was modded by Bob Thayer who has performed countless such Seiko and other watch modifications. Another such company is IWW, that I discussed here. Both shops do some amazing work. My recommendation is to use a relatively hardy but inexpensive watch such as a Seiko or Citizen when doing a custom project. Especially when you are unfamiliar with the results. It is enjoyable to experiment with various designs, especially when you can mix and match parts and pieces.
Best to start by purchasing an already modded watch to see the interesting result and then to start formulating you own ideas. You can get inexpensive and high quality watches (Seikos and Citizens) on eBay that are prime for being the base of such modifications. It can turn into an enjoyable hobby (if it isn't already one for you).
See Custom Seiko watches on eBay here.
See Custom Citizen watches on eBay here.
See MKII watches on eBay here.
See Seiko watches on Amazon here.
[...] the same individual who brought us this Seiko modded to look like an MKII watch, comes this newest creation. Before discussing this latest creation, it is good to know about the [...]