ðeɪ wɜːɹ ɐ dɪvˈɛləpmənt ʌvðə tˈuːhˈʌndɹɪd fˈoːɹɾi klˈæs, wɪð kˈɜːvd fɹˈeɪmz, ænd wɜː ðɛmsˈɛlvz dɪvˈɛləpt ˌɪntʊ ðə sˈɛvənhˈʌndɹɪd klˈæs.
They were a development of the 240 Class, with curved frames, and were themselves developed into the 700 Class.