In mid-1995 news came through that Saitek/Mephisto were replacing and upgrading the Saitek RISC 2500 with a new Mephisto product to be called the Montreux. It took some months for the Montreux to become available in the UK, and then only in small numbers. It had the new King 2 program from Johan de Koning (v1.00 dated 10th December 1994) on a larger 256 KB ROM. So the Montreux is a relative of the Tasc R30 v2.5. The other major change was a predominantly black case reflecting the style of other Mephisto plastic chess computers eg the Berlin Professional. Otherwise it was very similar to the RISC 2500 as the photo below shows. The Montreux was sold for £449 by Countrywide Computers from December 1995 but by the following Christmas it was nowhere to be seen in their Buying Guide, replaced by the Mephisto Atlanta.
So the Montreux arrived at just the time when PC chess programs were starting to dominate and top-end chess computer sales were drying up. With a sales period of less than a year not many of them could have been sold. This is confirmed by the small number that appear on Ebay, compared with say the RISC 2500. Perhaps one or two a year. So you would have to describe the Montreux as reasonably rare.
Using the Active and Offensive style settings can result in dynamic games with a strong emphasis on attack with sacrifices.