Paul:
Johnwill presented the Navy issue and I believe that to be correct. Most Navy models had longer barrels, but there is one that is presented with a 4" bbl, being Mfg'd in 1908. The 1908 Military, 1st issue, did not have the Stock Lug, There was however another Military Model, that was presented in 1914 that was the same as the 1908, except that it had the Stock Lug Added and the writting on/near the safety.
From your description, and the added information I believe that this is the model you have. To be absolutly positive, as Johnwill, mentioned, the purchase of the Lugar book would definetly be of assistance. Additionally, were you to secure an opion from a reputable Lugar collector would definetly be an asset.
It is difficult to detemine Lugar's without actually looking at them, as there were so many mfg'd. In my humble opinion, I think that your Lugar is the 1914 Military model. this again can probably be debated in the Lugar Books.
HJN