What does the term Mil-Spec mean?
I just searched for "mil-spec gold" on eBay and got 44 hits. This is one of my pet peeves so, please excuse my long rant. The term Mil-Spec, for gold plating, is often tossed around, erroneously, to indicate that the parts are of very high quality, as far as the gold thickness is concerned. That is absolutely not true. I'm not saying you're guilty of this, refinitman. I am curious, though, why you used the term and what you mean by it.
It was put into place, originally by the Defense Dept., I believe, to standardize the plating call-out for particular parts as far as thickness, purity, and hardness of the gold plating is concerned (also, it includes such things as what metal and how much of it will be applied under the gold - say, .000050" of nickel). For example, if the designer, whether military or commercial, decides that only .000020" (20 microinches) of gold is required, he will call out the thickness as Class 00 (see below). Mil-spec call-outs are used industry wide, both for military and commercial parts. It's just a way to make sure the parts are plated the way the designer wants them to be plated - that's all it means, period. Although many military components are plated thicker, for higher reliability, the term mil-spec doesn't mean these parts were made for the military, and it certainly doesn't mean that the gold is extra thick.
Mil-G-45204C Specifications
Type I: 99.7% gold minimum (Grades A, B, or C).
Type II: 99.0% gold minimum (Grades B, C, or D)
Type III: 99.9% gold minimum (Grade A only).
Grade A: 90 Knoop maximum.
Grade B: 91-129 Knoop.
Grade C: 130-200 Knoop.
Grade D: 201 Knoop and over.
Class 00: .00002" minimum thickness
Class 0: .00003" minimum thickness
Class 1: .00005" minimum thickness
Class 2: .00010" minimum thickness
Class 3: .00020" minimum thickness
Class 4: .00030" minimum thickness
Class 5: .00050" minimum thickness
Class 6: .00150" minimum thickness
Actually, I believe that the Mil-G-45204C Specs are officially out of date, although they are still widely used in industry. I think the spec that is now officially used is ASTM B488 which, incidentally, starts its list at .000010" (10 microinches). Also, I believe that other thicknesses can be spelled out, other than those on the list, and it would still be considered mil-spec if the Type and Grade were spelled out as by the spec. For example, you could call out Type II, Grade C, .000005" (or .000025", or whatever) - still mil-spec.
To summarize. The mil-specs concerning gold plating are simply an organized way for the manufacturer (or the military) to communicate to the plater, in a concise manner, the characteristics and thickness of gold they want applied to their parts - nothing more, nothing less.
Besides gold, there are ASTM and Mil specs for all types of plating, anodizing, etc.
I have considered asking the eBay sellers that use the term mil-spec, in relationship to gold plating, to define what they mean by it. I'm sure I would get all sorts of weird evasive answers. Most would have no idea what it really means. Most probably use the term because it makes it sound military and would therefore likely to be of higher quality than commercial parts.
Chris