The inscription means "syrupus croci" or "syrup of saffron (crocus sativus)."
"Infuse of the best English saffron 3 i. [one drachm/60 grains] in lb 1. [one pound/12 ounces] of canary. Let it stand close stop'd in a gentle warmth two or three days; then press out the wine, and melt it in sugar that is very fine 3 xx., which will give it a proper consistence. ... This is much us'd, and is expected to have all the virtues of the simple from whence it is made: it may be given almost at pleasure, and is much prescrib'd for children juleps." See J. Quincy, A compleat English dispensatory, 1718, p. 386-387.