Start with what the Alpina B5 (E60) is: a 4-door saloon (E60) / 5-door station wagon (E61) with 4.4 , built from 2005 to 2011, in the decade of stability control, dual-clutch gearboxes and the first serious hybrids. What it meant takes a little longer.
The background
The Alpina B5 (E60) is the first generation of the Alpina B5 high performance executive car manufactured by German automobile manufacturer Alpina from 2005 to 2011. Based on the BMW 5 Series (E60), the car was available in saloon and wagon body styles. The car succeeds the Alpina B10.
The engineering
The engine is 4.4 . On the scales it comes to 1720 kg. Drive goes through a 6-speed ZF 6HP automatic. The layout matters: a front engine drives the rear wheels, the classic proportion — long bonnet, cabin set back — that most people picture when they picture a sports saloon or a grand tourer. The wheelbase is 2890 mm. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Where it sits
In the Alpina line-up the Alpina B5 (E60) has a clear place: it replaced the Alpina B10 (E39); it handed the line to the Alpina B5 (F10); the factory was Buchloe, Germany. The cars a buyer would have weighed it against include the Aston Martin Vantage, the Bugatti Veyron, the Audi Q7. Its Alpina stablemates include the Alpina B10 and the Alpina B10 (E39).
Alpina B5 
Alpina B5 
Alpina B5