Greeting Kinsmen,
The easiest answer is light brown sugar or even brown sugar is the closest you
will find in a grocery store. Or raw sugar if you are willing to pay health
food stores prices. For the project.
Its an old term for sugar. That came in a slumped form after the solids was
drained of water. Out of a super saturated solution. It was cheap (er) than in
its more refined whiter form.
Your older recipt calls for it because it was less expensive and did the job
(providing fermentable sugars) the molasis in brown sugar will give very
similar effect in flavor.
Cheers,
Cnut