Unfortunately the .DAT file extension is too 'generic', all by itself, to mean anything specific.
Generally it is merely some Text file that some application wrote out as a file.
You can do a Google Search for DAT file extension and find where a wide variety of possibilities exist and that is merely some of the possibilities.
Additionally the .DAT file extension is often used by some Backup utilities to write out data into a 'generic' text format.
Therefore unless someone else recognizes the specific file naming convention you mention, I seriously doubt that these files combine to be any type of Database - maybe some backup of something, but not a Database itself.
And, due to the 'generic' aspect of the file extension, I doubt that you will get a definitive labeling of the type.
But perhaps you can 'extract' the data and use it in some manner.
Since it seems as though you have already opened one or more of the files to examine their contents, maybe you could 'extract' the data by identifying the layout.
You indicate that there are No Commas, but do the 'fields' appear to be in a standardized length format or have some other field separator - such as a Pipe ( | ) or Tab?