This article is from the May 1958 issue of "Radiotronics", the in-house publication of the AWV applications laboratory.
It gives a useful but condensed summary of the design fundamentals of vibrator power supplies.
AWV (Amalgamated Wireless Valve) was the valve making subsidary of AWA (Amalgamated Wireless Australasia).

[Note that Australian made Oak vibrators (manufactured by AWA under their MSP brand) operate at 100c/s. The reference to 115c/s is due to these notes
being based on literature from the U.S. based Mallory company.]

[While the information pertaining to the selection of timing capacitor is correct, there is more to it. If it was merely a matter of arc suppression, the value of capacitor would not be critical.
The timing capacitor controls the rate of polarity reversal of the collapsing magnetic field in the transformer, so that minimum current is flowing when the contacts are opening and closing.
Maximum current is timed to flow only when the contacts are actually closed. By this means, not only is sparking prevented at the contacts, but so is contact material transfer between the

For further information, see these links:

Mallory Fundamentals of Vibrator Power Supply Design.

Oak MSP Vibrator Notes.