Today, the definition of 'best' is largely conventional. Few people who line up for a Verdi opera at La Scala can explain what makes this music better than the opera written by a music professor of local community college and performed by the students of same college. They either feel the difference, or trust the experts which told them that Verdi is classic and community college performance is not. Likewise, few users, probably not one in a thousand, can really evaluate the level of quality that went into the gun, and to determine if it is a 'best' or not. The users agreed, with the help of experts, that certain guns of certain makers are 'best', and judge the guns accordingly. Reality is more complicated than "any Purdey is best, any Russian gun is a junk", although this rule of thumb does apply to most situations.

No formal attributes can define 'best'. Sort of like, the formal attributes of classical music are that it is written for strings, wood and brass. But not all music written for strings, wood and brass can be called 'classical', much less stand on the same shelf with Beethoven, Mozart or Tchaikovsky. Engraving especially has nothing to do with it. You can take a $200 Russian or Turkish gun, give it to the best engraver and cover all metal parts in the most fashionable style, and it won't make it a 'best' even for the respective Russian or Turkish factories, because they can do better than that.

'Best' is a thing of substance. "Best", roughly speaking, is what a gunmaker can do if price is not an issue. It means no compromise in every aspect of the gun. Beginning with choice of action - for instance, sidelocks have only marginal advantages over boxlocks (as far as price is not figured in), but a 'best' is normally a sidelock because the gunmaker doesn't want to lose even this smallest advantage. Same with choice of materials. Same with execution of all parts. For example, barrels must be fitted to action with such perfection, that if you drop a bit of oil on the watertable, close the gun, and it squeezes the oil out, leaving the watertable dry. Such precision is not really necessary for most sportsmen. But it is the absolute best any living or dead gunmaker can do, and for a gun to be real 'best', this is what a gunmaker must strive for. Same with meeting all requirements of the client. If the client want the right barrel to pattern in a certain way, you bore and rebore the barrel until it patterns this way and not any other way. Same with any aspect of gun and its making.

What makes it most complicated, is that 'best' is as relative as the speed with which you can run the 100 meters. For one nothing short of a world record is 'best'. For me, the best I can do is about 20 seconds, but it's my 'best' still. Same with gunmakers. What's best for some is only average for others.

W.W.Greener in "The Gun and its Development" (a book I highly recommend, a classic written in the golden days of Brit gunmakers when the concept of 'best' was defined) explained is this way. Most gunmakers can work to best standards. But few can sell their guns at the price level that would cover the expenses of building the guns in the 'best' way. So most makers must cut cost according to what they can sell their guns for, by putting in less labor, inferior materials, etc. This was written in 1880, but the general principle still works.

So, if you want to know if your guns are 'best' or not, there are basically two options for you. You can ask the experts (for example, uploading the pictures of your guns here), and agree with the majority. Or you can try to become an expert yourself, by reading, talking with people, and most importantly handle as many guns that are considered the world standard of 'best', and comparing your guns against them.