They made two models. Well two models and variations of the first model. The original carbine was a tube fed version that at first glance looks like a 10/22. I will no get into all the details, don't feel like typing. But mechanically they all were about the same with some minor internal changes through the production years. They were offered with various types of stocks. The early ones I believe around the first 3000 produced were stamped deerstalker on the receiver later ones were stamped 44 carbine. This was because of copyright lawsuit brought against Ruger by Ithica. As for them stopping production I have not heard any real reason. My suspicion is production costs. As they were popular throughout their production run of aprox 25 years.
Second version is the Deerfield carbine sometimes referred to as a 99/44. These look like M1 carbine slash Mini 14. Neat little gun that never was popular. I love mine. Biggest complaint I heard and the reason I think they were unpopular was the magazine capacity. These used a 4 round rotary mag. People wanted more rounds on board a semi auto.