They are indeed upon Fixed Centers. They use regular, old Spurs to affect the ratios that drive the lead screw that drives the quill out and back in, while turning and reversing.
Likely, but why guess when determining the reality of it is so simple? Just measure. Z+2/OD = your answer.
Z = Number of Teeth
OD = Outside Diameter
Example -
65 Tooth Spur Gear has an OD of 3.350".
Z+2 / OD =
( 65+2 ) / 3.350 =
67 / 3.350 =
20
The example gear is 20 Diametral Pitch.
Or....
Let's say the gear has an OD of 3.2972".
67 / 3.2972 = 20.32
Since it is possible but highly unlikely that the gears are 20.32 Diametral Pitch, we can try to see if they are Module Pitch.
25.4 / 20.32 = 1.25
1.25 is a very common Module Pitch size. So that gear would be 1.25M.
Or, to put it another way -
1.25 x 67 = 83.75
83.75mm / 25.4 = 3.2972"
Clear as mud?
Possible. But if it is Metric based, it won't likely be so simple. Why not just determine what they actually are and then purchase some commodity gears that might need minor adaptions to fit?
Good luck.
EDIT
If you do not have ANY gears, then simply measure the center distance of the two shafts and work backward from there. If you do not know how to do that and your Google is broken, report back and one of us can walk you through that, as well.
/EDIT