Given the line at the bottom and the vertical line at lower left, I would say this pair is from the upper right quadrant and you are 60% of the way to a gutter pair, but missing a very important part. Still highly unusual and seldom seen. At one time 634A existed in a complete sheet of 400..
The bar and wheel perforator produced the horizontal wavy cut when the rotary press printed paper web roll is cut into sheets of 400 (20 x 20) stamps. These cuts occur above and below the full sheet. Sometimes a horizontal line occurs with the wavy cut where ink got deposited between two curved plates of 400 stamp subjects. The sheet of 400 (20 x 20) stamps is then guillotined into 4 post office panes of 100 (10 x 10) stamps. It is along the middle of such a gutter (horizontal and vertical) that the sheet of 400 stamps is divided into 4 panes of 100 stamps. The gutters occur in between the 4 panes when they are all part of the one sheet. The rotary press stamp pane of 100 stamps below has the upper horizontal gutter trimmed in half while the right side vertical gutter has not been trimmed in half but broke off at the perforations of its adjoining pane resulting in a gutter snipe along its bottom gutters. On the horizontal bottom of the pane can be seen the wavy cut that separated the printed paper web roll into sheets which occurs on the side with the plate number corner. Such gutter snipes are more common on U.S. Stickney rotary press stamps than on Canadian Stickney rotary press stamps. So far, this is the only such Canadian stamp pane with this that I know of courtesy of a collector friend.