43psi is certainly an odd pressure guideline. I could see 40 or 45, but 43?. Also, that's super low for a max pressure rating even on a 2" wide tire. I'd expect a modern 70ox32c or similar tire to be rated foe 85 psi or even higher.
Here's some info that might be of help to you in determining the pressure you should ride it. Like all published data, don't take it as Gospel, but as a good starting place to be adjusted either way based on actual experience.
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