I have a 1941 Type R. The internal breaker does not protect every combination of binding posts. I used it for a bench supply also, having retired it when my parents gave me a ZW in early 50's. I recently re-retired it, and went to an MTH Z500 for the bench. It's adequate, cheap, and has a reliable breaker.
ON the ZW, do be aware that the internal breaker is in the line from one end of the secondary winding to the U terminals, so it would not protect against a short between any of the A-D terminals, which can occur is a train stops with rollers bridging a gap between power districts. For complete protection, I'd put a 10-amp external breaker in the Line from U, and a 7 or 5 in the ABCD lines.
