Summary

I created this solution several years ago to replace the coiner in an OK Baby cabinet, which often caused coins to get stuck. After removing the coiner, with this design, the coin falls directy to the microswitch.

EDIT: After extensive testing, I observed that the coins were falling too quickly, and the microswitch failed to detect them, resulting in no credit being registered. The overall success rate was 85%, but I achieved a 100% success rate using the design available at https://www.thingiverse.com/thing:3874393/ ('Coind duct for japan arcade machines').

Unfortunately, this design was too small for the OK Baby coin duct. Therefore, you have two options:
Remix the 'Coind duct for japan arcade machines' design making it taller.
or
Download and print "nozzle_for_Coind_duct_for_japan_arcade_machines_thingiverse_3874393.stl".

I initially printed thing:3874393 and, upon realizing the size difference, opted not to remix it. Instead, I modified my "nozzle.stl" to align with that design, but I had to use one bumper from DVDs/CDs bulks on each side to secure it in place.

I've shared the Sketchup project, in case that you want to modify the nozzle: "nozzle_for_Coind_duct_for_japan_arcade_machines_thingiverse_3874393.skp"