Piper PA 23 fuel cap part number CA16097N is an improved version of part number CA16097. This new part uses an improved elastomer with superior fuel resistance. The fuel cap is eligible for PA23-250, 23-235 aircraft.
Lever on cap top could be more sturdy, stainless steel instead of aluminium.
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Here is the application information for this fuel cap: PA23-235 & 250 SN: 27-1 PA23-250 SN: 27-4816 THRU 27-7554168
Per the supplier: Yes, these do have vent holes.
The distance you are requesting is approximately 2" in height.
Approx 2.5 inch diameter.
The application for this fuel cap is
PA-23-235 S/N#'s 27-1 thru 27-4815
PA-23-250 S/N#'s 27-1 thru 27-4916
PA-23-250 S/N#'s 27-7304917 thru 27-7305234
PA-23-250 S/N#'s 27-7305235 thru 27-7554168