Thank you everyone for your responses. I think I have been a little misinterpreted. I completely understand what gage pins and surface plates are used for and thank you for the examples of use, however other than gun making (thank you RGRAY) and my already mentioned watch and engine making I am not convinced I need either of these items as of yet. Sure, they are nice to have in the toolbox, but as for having on my want and needs list I have not been give good reason. I find I can still do all of the things that are described here with the measuring equipment I currently have, calipers, micrometers, and straight edges. As a hobbyist I am convinced that these are tools that I may want when I have more money than I know what to do with and an empty spot in my toolbox. I have a lot of other things I would want to spend my money on before adding them. And, I was not making any Snooty Job implications, you arrived at that conclusion all on your own. I did not intend to upset anyone here. I am just trying to understand if I actually have a need for these tools, and unfortunately so far you guys really aren't making the case. I am thinking that unless I get surface and tool post grinders, surface plates and gage pins are something I can (and so far) do with out. Again, these tools look like items that are more of a luxury for a hobbyist. Sure, I'll concede that the examples you are giving make the measuring process easier, but again, I can do it with the trusty measuring tools I already have. Sorry, just my conclusion from what has been presented so far. Now granted, I was making some of my projects with hacksaws and files prior to a mill purchase. Did I need a mill? One could argue that I didn't. And yes, it has definitely improved the quality of my projects. Other examples are CNC and Variable Speed Drives. Now, I do understand WANTS and this looks very much like these tools fit into this category. Also, one could make the case, my hobbyist machining is all just a want and not a need as well. HHHMmm, I think I just answered my own question.
Carry on everyone.