Ruger is in the business to sell firearms, not to make things easy for the collector/classifier, and they don't. What's in question is two separate and distinct Ruger models. I'll only address the stainless versions.
First is the model 00185, catalog KMK678G. It is roll marked "Government Target Model" on the right side of the receiver. Ruger has always maintained that this model received some special treatment. Most commonly cited are special sighting and chamber treatment.
The second is model 00186, catalog KMK678GC. It is roll marked "Competition Target Model" on the right side of the receiver. Ruger has never claimed that this model received any special treatment different from their regular target models, other than the receiver roll mark.
I think many people believe that the "G" in the catalog number is for "Government". I have seen nothing from Ruger to indicate this but I'm open to evidence. IMHO it's just as likely that it stands for bull barrel since the catalog number for the 6 7/8" tapered target model is KMK678.
Ruger has been consistent in using the "C" to indicate a slab sided bull barrel, so the "C" doesn't stand for "Competition".
The bottom line is that you can state anything you want or cite any sources (real or imagined) you wish when advertising an item for sale. It's up to the buyer to sort them out to his, or her, satisfaction. Based on what I see, or don't see, in the pictures with the ad, I would be uncomfortable with the price.