That rifle is definitely a CZ-557 and not the slightly older CZ-550? If so, it is almost certainly a prototype trial rifle offered to testing for the Rangers. The reason I say this, apart from the crest engraved in the exact spot where CZ usually puts engravings on rifle butts, is that that rifle has options on it that are not available so far on the standard commercial CZ-557:
1. Two front QD sling swivel studs;
2. Detachable box magazine; and
3. Iron sights mated with a straight non-Monte Carlo buttstock.
According to the CZ website, while the Lux model of the 557 does come with iron sights like the ones on your rifle, it has a walnut stock with a Monte Carlo cheekpiece hump. The straight buttstock like the one your rifle has only comes on the Sporter model, is made of beech instead of walnut (is yours beech or walnut or can you tell?), and that model comes standard without any iron sights and doesn't offer them as an option.
The Sporter model does comes standard with QD sling swivels, but only has one front swivel instead of 2 several inches apart.
The real kicker however, is that according to CZ itself, the company DOES plan to offer detachable magazines as an option for the 557 -- but not until 2014. The only 557s commercially available now have internal 5-shot fixed magazines.
Oh yes, and that sight mount for the scope is not a standard CZ commercial mounting either. CZ hunting rifles are usually offered with optional rings that mount separately into dovetails in the receiver (much like Ruger rings that fit into "notches"). That mounting you have looks like a variation of the picatinny rail system CZ offers with its Military/LEO 750 sniper rifle.
Add all that together, and that is definitely NOT just a commercial off-the-shelf CZ rifle that someone engraved with the Ranger crest as his own personal commemorative rifle.
BTW, what is the year of manufacture of that rifle? According to CZ, they stamp the year of manufacture on their weapons: "Pistol marks are located in a small oval behind the extractor/ejection port. It will be a 2 digit code indicating the year it was manfactured. Rifles generally have the manf date stamp on the right side of the action, slightly behind where the barrel threads into the receiver. The rifle mark is a proofstamp along with the 2 digit code."
You may want to try contacting CZ itself and asking them about your rifle's history. You could start with CZ-USA at the following email address:
info@cz-usa.com.