We bought our 91 SE-R new in 91. The odometer quit working a year or so later at 15k miles. I can't remember the name of the dealer in Jacksonville (Atlantic Blvd by Regency area) but they installed a new one but wouldn't set the mileage to 15k, instead they left it at zero.
But then again, they were the same dealer who told my wife & then me that I needed a timing belt at 50k miles on my SR20DE.
I asked that they give me a quote in writing, funny, never heard back from them.
Your mileage doesn't sound out of whack to me. Call Infiniti customer care & they can retrieve the archives on the service records on the car & tell you if there's been any work done by a dealer.