Based om conversation and the reading I have done:

No. No one can post a picture of a boxlock "Best Gun". That is an oxymoron; guns with boxlock actions are not Best Guns.

Also, a Best gun is not: guns that were the best each company had to offer.

The phrase "Best gun" was developed within the trade to describe a level of the gunmaking art/trade; it is a description with very little room for interpretation.