Pioneer made and sold vertical cylinder saws from 1946 to around 1971. I don't think they made a horizontal cylinder saw until the mid '60's.
Fossil, you are correct they did under their IEL patent designs going way back to 1946 with the IEL Beaver the world's first 1 man chainsaw. But the company was IEL , Pioneer was their saw's model name.
OMC bought out IEL in 1956 then changed the company name to Pioneer in 1958 . They kept that IEL verticle design with the HC JC Ra etc. right up to 1964 with the 600 650 850 etc.
Then in 1965 they left the IEL patent design and went with their own horizontal cylinder to copy the 1964 Homelite XL.
Great company back in the day even into the 1980s joined up with Poulan, Partner under the Electrolux roof.