Racers definitely came online toward the end of 1955. I have around 20 racer examples archived from 1955. The 1955 ones always turn up with a different downtube decal. Same one that pops up on various other models in the 50s, but was only time used on the racers. 1955 ad below.
The deluxe racer always had stainless fenders. The regular racer has painted ones. So two things are going on with this bike: 1) someone swapped out painted fenders for stainless ones (very easy to do and many have done that); 2) someone swapped out the chain guard from the Deluxe Racer one to the regular Racer one (which seems unlikely). There is also a difference in stem type I see on the Deluxe racer which is more consistent with the higher end lightweights and you would see on the traveler and middleweights. Yours has the lower end version. Other than that not really a good way to tell them apart as I have seen multiple speeds and brakes on both versions...
So back to your question, because of the decal not matching what is typical of '55 examples and it being an earlier '55 frame stamp serial, and the lower end stem, I would say it is not Deluxe and more likely a '57 with swapped out fenders.
Also, never seen that 5<>6 stamping...