While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of 3D Systems (NYSE:DDD) gained about 2% this morning after Jefferies assumed coverage on the 3-D printing technologist with a buy rating.

So what: Along with the bullish call, analyst Jason North planted a price target of $67 on the stock, representing about 26% worth of upside to yesterday's close. So while momentum traders might be turned off by 3D Systems' sharp year-to-date pullback, North's call could reflect a sense on Wall Street that the company's growth prospects are just too cheap to pass up.

Now what: Although 3D Systems is no longer Jefferies' "Top Pick" in the sector -- that honor now goes to Stratasys -- the analyst thinks its risk to reward trade-off remains attractive. "3D Systems is the most complete player in the 3D printing industry today with an offering that spans software, service bureau, consumables, and the widest range of printers," said North. "Our checks indicate that 3D printer sales to manufacturers are likely to increase due to greater developmental/research purchases as more companies investigate 3D printing." When you couple that upbeat outlook with 3D Systems' cash-rich balance sheet and beaten-down stock price, it's easy to understand Jefferies' bullish stance.