I'm currently trying to replace the mortise lock and electric strike on the front door of my building and need help!
The electric strike appears to be quite old and I'm having a hard time identifying a replacement for it. See below for a picture of the strike - any help in identifying what it is / a relpacement would be greatly appreciated!

Other than that - I'm pretty sure if identified the appropriate replacement for the mortise lock/knob itself - an Arrow AM01-BG Passage Mortise Lock.
Below are a couple images of what is currently installed:


The only thing that is throwing me here is the "BG" portion of the lock type. Can somebody explain to me what the difference between "BG", "BH", "HBG", "HTG" etc..is?
Thanks.