Salvete!
I wonder if you have ideas about this abbreviation found in a 16th c. nautical text (Quatri partitu en cosmographia prática). The text is in Castilian, but the author likes to sprinkle Latin ligatures.

I'm thinking "sive", but still not quite satisfied.
“...tienen fuerza principalmente en verano sive primavera y en otoño”
I've already tried this excellent Mexican dictionary, to no avail.