Is the calligraphy Ode to Shimen official script or regular script? Which dynasty did it belong to?

Ode to Shimen. Han dynasty official script, cliff stone carving. Originally written by Taiwei in the early years, the full name is Ode to Taiwei in Li Si, which was engraved on the west wall of Shimen Tunnel at the southern end of Baoxie Road in Baocheng, Shaanxi Province in the second year of Han Dynasty (AD 148), with a height of 26 1 cm and a width of 205 cm. Carved 22 lines, full of 3 1 word. Knots vary in size, the brushwork is thin and unrestrained, vigorous and comfortable, quite interesting, more clever than clumsy, like to use growth, with a round pen.