That's what I was thinking. , after reviewing
Oilit's post and link to others, It's not a 55 and had to be a 1954 >>>> 08/07 to 08/08 ------- L85454 ------------------ L97650
http://re-cycle.com/History/Schwinn/SwnB2_Serial.aspx#1954
And I wouldn't call them a Prototype, but 1st year production model. which should be in the area of mid summer 53 to end of summer 1954 'Back to school' sales/production.
With yours being this late in 54 it's likely of the last model like it made B/C they would also be producing the newer middle weight 55's at this time too.