splash screens are installed separately via JSGME. Having an aftermarket splash loaded does not mean you are running a mod, nor does having the stock splash mean you are not running a mod.
There are lots of ways to see what database is active, but I would imagine the easiest is to go to the USNI and load a platform that doesn't exist in stock DW. E.g., just off the top of my head, the Astute SSN for the UK. I don't think USNI can reference a model unless the proper database is active.
Before we expanded the USNI I used to say to shoot an SS-N-27ASM and see if it sped up (stock) or fired a 2nd stage (LWAMI).
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