Congrats on your find, it is hard to ignore a lonely looking 657.
There were a couple on Gunbroker the last month or two but they do not show up very often.

My letter from Earl Minot at Lew Horton states that there were 202 units produced in 1998; 115 units with HRC prefix and 87 units with HCH prefix.

Other versions of 657s that were produced can be seen here 657-41 Magnum-Lew Horton-RSR-Davidson's-Dealer Specials and Regular Production

KO