For paperwork purposes, I believe you will have to determine how the prop was marked by the maker. Different prop makers use different standards when it comes to determining the pitch of the prop, so measuring it directly from the prop will get you close but likely not exactly right. Measuring it might suggest that the prop is a 60.5" pitch, but the maker might have originally listed it as a 60" or a 62" (or something else).
If you took pitch measurements from the prop and then could talk to the prop maker, likely they could tell you what the pitch is. Unfortunately, I believe Warnke is no longer making props. It was a family business, but Bernie (?) died a few years ago. I think his wife attempted to take up the business for a while, but I've read that the results weren't so good. Someone else may have a better update.
Since you may not be able to get in touch with Warnke, another idea would be to measure the pitch directly and then compare it with other Warnke props. You'd have to find other Warnke props to compare to, which might actually be harder yet.
Finally, it's quite easy to pull and reinstall a prop. You'll need a good torque wrench, the right socket and wrench, the correct safety wire, some diagonal cutters, and a pair of pliers (to twist safety wire). If you don't have a spinner, you could probably pull and reinstall the prop in less than an hour - even with a spinner. If you don't feel comfortable doing it, a competent mechanic could do it easily. Be sure to maintain the same clocking of the prop and crush plate when reinstalling.
Regards,
Matt-
