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That set has been around a long time. As I understand it has been around off and on from the 70s into the 90s. The early sets would be AC and 25 watts sounds about right.
Looks like a decent little O-gauge starter set. But just so you know, it is indeed an inexpensive starter set. Equipped with inexpensive components. But that was to make it affordable for most folks, which is the intent of all starter sets, no matter what the scale.
Lionel has also always made higher quality (and as a result, more expensive) trains and starter sets. For instance, your steam loco appears to have a plastic-shelled boiler. Get into some slightly more expensive steam sets, and you will find the boilers are die-cast metal, and have much better, heavier duty running mechanisms And some even have die-cast metal tender shells. Freight cars are sometimes better quality, and may include die-cast metal, sprung trucks. Passenger cars likewise for the most part, along with having interior lighting. Transformers included in these sets generally have a higher wattage rating to allow additional power for various accessories.
And we won't even talk about their top-of-the-line model train offerings. You know you're in the big leagues when some of their best steam loco offerings cost more than some used automobiles do!
Like I say, what you have is still a nice little, affordable starter set. Just don't mistakenly think it's indicative of ALL O-gauge trains.
Have fun with it!