Help with vetting 1920s cushion Rolex

[whatcha]

I am looking at a listing for a 1928 rolex oyster and would love to check your collective expertise if any red flags?

I'm still in the newbie phase, but the only thing listed as "original" is the dial. As such believe the crown is not original as it should an onion crown instead - is that correct?

Any other red flags in terms of authenticity of the movement etc?

Thanks in advance!

Description below and photos attached:

A RARE HALLMARKED 925 STERLING SILVER 1928 ROLEX OYSTER '563' PRIMA 15 JEWELS ADJUSTED 6 POSITIONS WRISTWATCH

THE STERLING SILVER OYSTER 'CAMBRAI' CASE IS 35.6mm WIDE INCLUDING CROWN AND 36.59mm FROM 15mm WIRE LUG TO LUG.
THE CASE IS IN OVERALL GOOD CONDITION WITH SOME MINOR USE MARKS WHICH COULD BE POLISHED OUT IF THE BUYER DECIDED.
THE OYSTER SILVER SCREW BACK INNER IS STAMPED ' ROLEX 20 WORLD RECORDS WITH ENGLISH, US & SWISS PATENT NUMBERS' IN ADDITION IT CONTAINS A 'DOUBLE PRONE F MARK' GLASGOW ASSAY OFFICE IMPORT MARK. 925 (SILVER PURITY MARK). DATE LETTER f (1928). RWC (ROLEX WATCH COMPANY). CASE REFERENCE 563.
THE WHITE ENAMEL ORIGINAL DIAL IS IN PRISTINE CONDITION FREE OF HAIRLINES OR CHIPS. THE DIAL HAS PRINTED ROMAN HOUR NUMERALS, OUTER RAILWAY MINUTE TRACK. IT IS PRINTED 'ROLEX OYSTER SWISS MADE' FITTED WITH BLUE STEEL 'BREGUET MOON' HOUR, MINUTE AND INSET SUB- SECONDS HANDS.

THE 15 JEWEL MOVEMENT PLATES ARE STAMPED '15 JEWELS TIMED 6 POSITIONS FOR ALL CLIMATES SWISS MADE'
THE WINDING WHEEL IS ENGRAVED 'ROLEX PRIMA' THE WATCH KEEPS GOOD TIME WAS SERVICED SOME LITTLE TIME AGO. THE SCREW DOWN WINDING CROWN IS MARKED PATENT OYSTER.
THE LATER HIRSCH BLACK LEATHER PADDED GREY STITCHED HIRSCH & LINED 15mm STRAP IS FITTED WITH A LATER ADDED ROLEX CHROMED BUCKLE WITH CROWN. ALL IN ALL THIS IS A LOVELY EXAMPLE OF A HIGHLY COLLECTABLE ROLEX.
PLEASE SEE MY OTHER CONTEMPORARY ROLEX SEPARATELY LISTED.

[adam78]

Interesting...I just acquired a very similar one this past year. Yes, I believe both would have had an onion crown, and these appear to be early service replacements (pretty common). Although they look identical, the case references appear to be different. Some of the early ones I think did not yet have SNs.