Nice machine.
Gritzner's are very high quality German machines. The "badge" is actually from the importers. My Frister & Rossmann's like this have one from 2 different London importes. I have not seen a Singapore importer badge before, that's cool!
It looks to be from the 1910-1930 era. They have serial numbers like Singers in a similar location.
While I am a hard core "American Made" kinda guy, I have to admit that my German machines are the best machines to work with in my collection. Especially my F&R Modle E which is very similar to this one but with full reverse capability.
Pricewise, this one is reasonable. Not a "good deal" Not TOO overpriced. I'd try to get them down to $150 by offering $100 with cash in hand first.