here are two other auctions for the same part number, also oddly cheap,
6110347 is a Model F part number, and maybe by 1989 the refurbisher thought that the "Model M" mark would have a bigger market recognition.
$70 shipped for missing keys and damaged case and $97 shipped for a complete specimen might be a bit "low" but not "oddly low" considering how many of these have hit the market in recent weeks.