Just an opinion based on over 35 years messing around with many, many, Uberti's...
Think they went 1,2,3 on each model in their earlier years... it is possible they sometimes started over when reaching a milestone like 100,000. I do not think they did small batches of numbers like 1 - 100, 1 - 1,000, etc.
Uberti may have started at 1,2,3 on a production run for Navy Arms, Western Arms Corp. (Later Allen), etc. where the guns had Uberti markings and importer's company name...
From memory, an 1860 Colt, Navy Arms & Uberti marked I got second hand in the mid 1970's had a capital A prefix on the serial number: A67XXX
Looking at:
1. An older Pocket Navy .36, marked Navy Arms & Uberti... it has serial no: 88XXX
2. An older 1860 Colt .44, marked Western Arms Corp. Santa Fe N.M. & Uberti... it has serial no: 109XXX
3. A newer Uberti cap & ball stainless short barrel Remington .44... there are only Uberti markings, no importer. On the butt it is numbered: A46XXX
Am not able to get more Uberti's to look at as am at home & most guns are stored elsewhere. Several early 1851 Navy, Navy Arms and Uberti marked I do not have at hand are marked with just numbers, no letter prefix. These are early plain cylinder models.
Your gun is very interesting with a single diget serial number. What model is it? How is it marked? Is your gun marked both Uberti and Navy Arms?
JMO based on many years experience, hope this helps but perhaps we have raised more questions.
Any Uberti experts out there?