I think the gun here is an unsual 4" Officer's Model ...? I'd bet a ham sandwich and cold one that Colt didn't make the OP w/adjustable sights. I suppose it could be a custom job. I've only ever seen one 4" OM.
I have a 1933 vintage Officers Model with a 4 1/2"bbl. on the table before me. This,as has been said,is NOT an Officers Model. While the sight has the dovetail appearance,I can't see the adjusting screw protruding through,and front sight,while not a "ramp",sure has,as dfariswheel says,"the added on look";but looks like it has(hopefully)some height adjustment. All this said,if I saw this piece in person,and could see that it functioned fine,lock up etc,and good bore etc.,I would buy it at that price. The seller is honest,he says it is an Official Police. If it in great shape,it would be a fine shooter,and by looks of grips and thumbpiece latch,its a "pre war".And just by the "off chance" thats its a custom job by Christy etc.you'd have a collector piece(But custom revolvers are hard to sell for a fair price!) The photo is NOT a good image,and sometimes they can be "deceptive". Final advice,if you want a shooter,cant find too many pre-war O.Ps for under $200!,plus the seller has the 3 day return deal. Bud