You are right, the MR-7 came out in the mid 90's. They were only available for 3 or 4 years. MR-7 sold like hotcakes at first then died a fast death. MR-7's did not have a faithful following after the first round of buyers, as is the case most of the time with new editions.
MR-7's came out in .25-06, .30-06 and .270. If Marlin made any other calibers in the MR-7 I don't know of them. Marlin could have.
The MR-7 Copied designs from a few of the manufacturers of the time... Ruger, Remington, Winchester and Browning. The Magazine was a copy of Browning, The bolt was a copy of Winchester. I believe the Receiver was a copy of Remington. I don't know where Ruger comes into it. But Ruger is there somewhere.
I bought two of them when they came out. My MR-7 .30-06 is the most accurate rifle in my cabinet and is my pride and joy. But it took alot of gunsmithing to get it to this point. My gunsmith told me if he charged me for all of his work, I could easily have doubled the price of the gun at the time. He did not charge me full price as it was the first MR-7 he saw and he wrote a Letter to Marlin detailing the problems with the rifle. Which Marlin acknowledged and thanked him for. I paid for a trigger job but got full service.
Up until last summer the MR-7's were readily available for roughly $369 +/- on the Auction Sites, which is just about what they sold for. That has changed drastically. Even though they are still available from time to time, the price has gone up for NIB examples.
Not oddly enough, it is the gun nobody wanted that gets the attention. I doubt the MR-7 will get the attention the Marlin 55 Bolt Action gets, but the MR-7 will never be sold at a loss.
One day I will sell the one MR-7 that I never opened to recoup the cost of both of them.