That's a VERY fine find in surprisingly fine condition...all the more wondrous for it's hopping out of the dirt in New Jersey. It's not particularly valuable--maybe worth $20 to $40 on a good day--but it still carries with it considerable historical baggage worth quickly rummaging through.
A "Denga" (pronounced more like the game "Jenga") was pretty much the basic bedrock coin used for small transactions in the Russian empire, roughly equivalent to the half penny or "ha'penny" (pronounced like "HAY-penny") of Britain and its colonies or the 1/2 Kreutzer of the huge Austro-Hungarian Empire, which bordered much of the Russian Empire. In fact, the design of the Denga you found on the side with the date so very closely resembles that of its Austrian equivalent of the period as to be nearly identical, as shown in these examples:
The "Denga" was such an important traditional denomination in the Russian Empire, derived from its mediaeval Tartar/Mongolian invaders who minted them in silver, that even nowadays, hundreds of years after the last "Denga" coin was minted, the Russian word for "money" is still "Деньги" [= "Den'gi"], simply being the plural of "Denga".
How your find may have found its way to New Jersey can only be surmised. I might expect that its very close resemblance and intrinsic value similar to the likely far more common Austrian 1/2 Kreutzer coin may have played some part. in the Colonial and even Post-Revolutionary economy of America, where small change was often in extremely short supply, foreign coinage and even privately-minted tokens of many types often circulated, alongside and on intrinsic par with official British and later U.S. coinage. In fact, the "Spanish Milled Dollar" or 8 reales, from which we derived our own dollar, and its smaller denominations remained legal tender in the U.S. until just before the Civil War. Such currency scarcity is where we get the old term "two bits" for a quarter or 25¢, because such Spanish dollars were often cut into eight parts like a pizza to make smaller change available--hence 2 bits equaled one quarter.
So my hunch is that what you've gone and dug up there is an honest to God American Colonial Relic. To put it into Colonial economic perspective, at the local tavern it would have got you a pint of "small beer" (local homebrew) in a pewter mug that Ebenezer your Publican (
i.e., "barkeep") would have thoughtfully spit on and wiped clean with a calico rag for your better enjoyment of his draught. So, you'd do well to take that rig of yours back to wherever you found your "Denga", and see if you can't find that mug too!
Seriously dude, well done indeed!