The letters of the typewritter is dissapear it just the lower letters. Not very clear.....

your typewriter was built in early 1939

has someone changed the keys around? compare it to the qwerty keyboard on yr computer and see if the letters are in the same locations to check

Download the manual @ brother.com, click on support.

DickyO

Possibly the lower edge of the ribbon has become folded over during fitting, it happens.

open the lid and look inside by the ribbon, see if it there is a red switch that has been slid over to S

A typewritter is not like a computer. It is a mechanical device, that works by pressing an embossed letter in the daisy wheel through a inked tape into the paper.
The only way you can change either the font type or the font size is by buying and replacing the daisy wheel by another one with different font type/size letters.
To get to know more about your typewritter and accessories that might still be available to it, download Brother ML-100 Typewriter User's Manual
Click on "Go to View/Download Page" and in the new page click the "View/Download" button.
Look for page 16 (last page) of the manual for a list of cassette daisy wheels.

do you see any impression of letters on the paper when you type? if you do the ribbon not lifting or not driving. If you do not see an impression the print hammer is not firing. try to lub it with wd40 or light Wait oil. some brother typ's have a rubber bumper under the print hammer that deteriorate & need to be replaced

The cartridge just snaps on, printing half letters may be caused by the ribbon being folded over on itself or not moving look at the ribbon toward a light you should see each letter clearly thru the ribbon

After you press the corr. key you must retype the wrong letter then type the correct letter.

DickyO

Selectric I and II type elements are identical (88 char) where Selectric III uses a different element (96 char). The 88 character element will have white lettering and the 96 character element will have yellow. Directly underneath the lift-up tab to remove the element will be a 3-digit number. That's the last 3 digits of the element's part number, which will be preceeded by 1167 for 88 character, or 1352 or 96 character. For example, if you have a '052" stamped on the element, and it's an 88 character style, the P/N will be 1167052.

The correcting mechanism is an intricate additional function of the backspace function. To test it/adjust it/or repair it requires the machine be hand-cycled using a hand cycle wheel which is screwed into the right hand side operational shaft. It's unlikely that an un-trained party would be successful repairing this..