Since Daytona has already been discussed - I won't mention Daytona
(and outside the fact dials can be swapped)
popular sport models:
Yachtmaster: if it is ALL steel looking (dial and bezel) it probably is the Platinum model. Anything else is probably SS or YG.
Submariner: If the bracelet looks like all steel and the dial and bezel is blue.. then it's white gold. All others will be SS or YG. (no Platinum)
SD and DSSD: probably just SS.
Any other models with all steel looking sport bracelets will be SS.
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In short there are very few white gold and/or platinum sport watches. (outside of Daytona)
Best advice is first identify which model and tell us what color the dial is (and bezel)
this link has a good list of watch and descriptions and what they come in.
http://www.bernardwatch.com/Rolex-Model-Overview