It is indeed a sporterized M1941 Johnson rifle. I couldn't tell from the photos whether or not it was done by Winfield Arms, but that company sporterized a large number of Johnson rifles. However, it doesn't look like the typical Winfield conversion and it may have been done by an individual gunsmith. The "presentation" rifle story is fantasy. All M1941 Johnson rifles were made under contract for the Dutch government and Johnson Automatics did not make any "special" or "presentation" Johnson rifles.