The Medallion STAMP is a way to, in effect, notarize the transfer document. It's only available from brokerages, and BMO. For BMO, you have to have been a customer for some period of time or they won't do it for you. The STAMP is only at certain branches and only certain employees are allowed to use it. They confirm your identity, then stamp the form.
NOTE: This is a bit of an esoteric operation for a customer-facing employee, so you may have trouble even getting an employee to understand what it is you're asking for.
The other Big 5 banks have a system of signature guarantee for the same purpose; certain bank employees have their signature registered in a book which is provided to/updated with the transfer agents at some frequency (once a year perhaps). When such an employee signs the form, the transfer agent can look up their signature in the book as a verification, and then trust that they confirmed your identity. I think this system is called "Signature Guarantee for Securities Transfer".
NOTE: There are a number of signature guarantees for various purposes, it's pretty easy for an employee to give you the wrong one.
...Stu