Oki LD670 Mode D'emploi page 95

Then, press and hold down the FEED switch for one second or longer to
accept the selection. The printer prints the following when you accept the
selection of "MAX SPEED":
7. Select "9th" as your option.
Press the FEED switch briefly (one second or less) until "9th" is reached.
Then, press and hold down the FEED switch for one second or longer to
accept the selection.
5th
9th (High Speed)
8th
7th
6th
5th
4th
3rd
2nd
1st (Low Speed)
Selection Item
Max Speed
9th (High Speed)
↑
8th
↑
7th
↑
6th
↑
5th
9th (High Speed)
8th
7th
6th
5th
4th
3rd
2nd
1st (Low Speed)
Selection Item
93