When I contacted John Langdon about my Gritzner, although he said he didn't know a lot about German sewing machines, he sent me this on dating mine:
"German machines were not well documented at all.
The most common way of dating them is spotting an advert that says "This
year we will have made a million machines!" - take the year the company
started away from the year of the million sales announcement. Then divide
a million by that number and you have a rough calculation of how many
machines they made per year. Not accurate, but a rough average.
With Gritzner (million sales in 1901), it worked out to 91,000 per year.
Take your serial number away from 1 million (the first serial # if there
are two), divide the remainder by 91,000 to give you a number of years;
then take those years away from 1901. It's all a little bit vague as some
people say Gritzner achieved its one million sales in 1902 - I don't know
off-hand.
Gritzner achieved two million sales in 1910, I think."
I hope this will help you in dating yours. I'm still not to sure about mine as where the serial number is, there is a 7 a little farther after the rest of the numbers ad down a little on the plate. Did either of you find this with yours? I'm wondering if that 7 is a model number or something like that rather than part of the serial number. Without it, mine is from 1891, and with it, 1898. Anyway, I have an ANTIQUE sewing machine along with my vintage ones!
Janis