Sears had manufacturing agreements with several manufacturers, including Winchester and Marlin. Do a google search on Sears Rifles and you'll find some info. The rifle your friend has was probably made by Winchester. I found this on the net...
Sears Model 53
Q: I am curious about a bolt-action rifle I acquired recently. The barrel is marked "Sears, Roebuck & Co., Sears Mod. 53, Cal. .243 Win." A friend told me it was manufactured by Winchester for Sears. The rifle has a Bushnell Banner 3x9 scope mounted on it. With 75-grain handloads, it groups under an inch at 100 yards. I am planning to use it for deer this fall with 100-grain bullets. Can you tell me something about it? --G.S., Phoenix, AZ
A: Your Sears & Roebuck & Co. rifle was manufactured by Winchester and is basically a Model 70 that was subcontracted by Sears to compete at a lower price point. These types of subcontracted rifles typically make great shooters and today are priced considerably under the major trademark models from which they are derived.
I thinkthe only real difference between the Winchester and the Sears versions was that the Sears version had a cheaper/plainer stock.