Very nice Myler Toklat bit.  Believed to be an MB12 with a 5" mouth and 7" shanks.  Sweet iron mouth with copper inaly oxidizes and encourages salivation for a soft mouth.

The MB12 is a solid Level 3 ported mouthpiece.  The tongue pressure that the horse feels on the outside edges of the tongue is mild.  The port on this mouthpiece is approximately 1 ¼", so it will apply little to no palate pressure. Suitable for a  finished horse that requires the occasional very mild reminder. It lacks Independent Side Movementâ„¢ so it has a more solid feel and shows less rein movement.