Thanks Jon,
I did find one on the net today with a s/n in the 136000 range and it was said to be an 1891 slim. If it's true then it's possible that mine could have been made prior to 1900. The tension is not the metal disk, it's felt and you need to wrap the thread one and a half times around and the pitman arm is made of wood. These two items may indicate an pre 1900 machine. The manual is undated and I have a service receipt dated 10-17-1972 serviced by K.R(KEN)Kinstler, Jr. in Clyde, N.D. He cleaned & adjusted the Standard for $4.75 and 2 hrs. labor @ $2.00 per hour on ticket #41 was $8.75!! Wonder if he is still in business?
Rodney