I know quite
a bit about these rifles so now I have to type a lot to help you.

Really, I want to. Okay, this is a summary about these rifles. I may be a bit off on some facts but not much. Not to brag, it is just that they are one of my favorite models.
The Ithaca Co. started selling this rifle in very late 1961. It was obviously aimed at the boy's and girls market. Single shot, very safe, have to cock the hammer to shoot. They sold for about $20 originally. They were made to look like the Model 94 Winchester to capitalize on the big appeal of cowboys, etc. back in those days. The tube under barrel is a phoney magazine for looks. They were made until about 1978 I think. There were a lot of them made but a gun show dealer told me they still sell really well when one shows up. The receiver frame is made of anodized aluminum, it is NOT blued steel. Not many years after they came out the wood was switched from walnut to grey elm. Also, at some point in time, the butt stock and sometimes forearm had pressed checkering. Also, almost from the beginning there was a deluxe model with figured walnut stock, better finish, gold plated trigger and hammer with sling and swivels installed. There was also a presentation model that had really nice walnut and a personalized engraving by the company engraver at buyer's request.
Eventually, the original model that had the phoney magazine tube fastened by a barrel band that also had the front sight was changed to a different version with the magazine tube dovetailed to the bottom of the barrel and the barrel was a bit longer than the mag tube.
At some point they made 22 magnum models of this gun. Quickly it was realized that some way must be made to quickly identify the two different calibres so Ithaca started using a white butt stock spacer between the butt plate and stock. This quickly identifies as a 22 magnum.
As said, they stopped making them in about 1978. However, for a brief time at some point Ithaca made a Model 49R which was a lever repeater. This, I believe was a very cheaply made gun and only made for about 3 years. It was replaced by the Ithaca Model 72 repeater which had the gun itself, perhaps not the wood, made by Erma Werke in Germany. This was a good gun I think.
Now, Ithaca made a model for Sears of their 49 that is identical to the 49 except the phony magazine tube was left off. I forget what model it is called but I think it had the Ted Williams Sears brand on the barrel.
In the late 1970s I believe Stevens started making a 22 that is about the exact twin of the 49 with very slight differences. It is the Stevens Model 89 and was made for about 7 years I believe. Same type frame/receiver with anodized aluminum alloy and their wood was simply inexpensive hard wood with a cheap looking finish. I have one and have refinished the stock. I also own an exact clone fo the Stevens 89 made for Western Auto with their brand name Revelation on the barrel. However, the roll stamp also shows that gun is made by Savage/Stevens.
These little guns are rugged and yours should give your son and you loads of enjoyment. Hours and hours and thousands of rounds of shooting.
I envy you finding such a nice one with walnut stock. I have a very nice Ithaca 49 I bought a few months ago (I had a 20 year lapse in guns so getting back in at age 63) but most of the ones you see that are nice have the grey elm wood and I want a gorgeous walnut like you found.
Around here in Iowa and on the internet it seems that a rough model of these runs about $100 but a nice one will be $150-165 at a shop or gunshow.
About the anodized aluminum....the black coating will eventually start to rub off some with use. This will not hurt the gun and it will NOT rust (The steel parts will of course). There are touch up products for aluminum gun receivers and I think Brownells sells something even more sophisticated that you put on after warming the metal up to over 100 degrees. But the nice one you have certainly needs nothing like that.
About better sights...there is an old Ithaca 49 ad that shows a boy scout shooting that gun with a receiver peep sight (See entry above)on so the implication is that a receiver sight could be mounted. I am thinking about checking into this eventually. Also, there is an article in a 1970s Gun Digest about shooting 22s and the author wanted a scope on his 49. He said gunsmiths were hesitant to drill into the aluminum receiver but somehow this author did cobble together some spit and bailing wire mounting and had a small scope on his 49 for squirrel hunting.
My nephew, who is a much better shot than me, was shooting at a hundred yards I think with mine a few months ago and was getting within about 4 inches of center of bulls eye repeatedly with these old, open iron sights.
I hope this helps. Darn, I would love to find a pristine 49 with walnut furniture.
Also, the action is technically a Martini action with a rebounding hammer. And, of course, later models, after about 1968 had serial numbers. The standard reference on Ithaca guns, I forget the title, tells about this neat little rifle.
One more addition: I forgot to mention that this could also be obtained in a "boy's model" with a shortened butt stock.
LATE ENTRY of 9-26-06...With reference to the Stevens 89 I just found an article in American Rifleman of Sept 1976 that old about the "new" Stevens 89. In a detailed review explanation about that gun it stated that the receiver/frame is made of "cast zinc alloy with epoxy coating." Now I do not know if this indicates what alloy the Ithaca 49 frame is made of but we now know about this model.