I have an interesting 1 of 5 non-serialized Cuban muskrats in antique green jigged bone from 2007,
of which they made 125 serialized knives.
Only time will tell if it commands a higher price.
And if it does we'll all buff off our serial numbers and etch
I have seen some that would advertise the non-serialized in a run of 50 serialized + 5 non-serialized as "Only 5 made". Simply an ethics issue.
Many times the factory uses parts on hand to decide how many they will make, and many times they gauge distributor demand. Unless they are making 50 or more of a variant, they will not serialize them. And generally they serialize the first 25. So, as a rule, there are at least as many non-serialized as serialized in a run. Also, the serial number has somewhat lost its glimmer and most will just pocket the extra money. Stag and some other special situations change this a little; but this has been a factory policy for a while.
Now, the one exception to the value of non-serialized was the 2006 models. In 2006 they did not start the serialization over when they changed slabs. So, if they made 400 Tidioute #73 models, they may have been (don't have the actual breakdown) serial #2-60 = Bocote, #61-130 = Chestnut bone, etc. And once they finished all 400 planned knives if there were more Tidioute blades and frames they would finish them out. But this number was very small and generally only one slab choice as they would go on the first ones until out. So, out of 1400+ knives, there were probably less than 2 dozen non-serialized (and no difference in price). So, very quickly some of the savvy collectors picked these up along with a copy of the factory invoice showing non-serialized delivered to that distributor. So in 2006 models you had only the #73 and #23 frames, in each the Northfield and Tidioute brands. So only 4 distinct serialized runs.
In 2007 they planned to serialize them all as well, but they had overruns sometime in more than one slab. So the non-serialized in 2007 were a bit more common. But without a factory invoice to a distributor and your invoice from the distributor both stating a non-serialized it seems somewhat useless. As someone with a little experience with a buffer could turn a serialized into a non-serialized relatively quickly. The high dollar writings of Chris Tucker on the label then would be the only tale-tell sign.