Based on the serial number you provided (No70688), your Epiphone guitar is likely from 1968. This is because Epiphone used a sequential numbering system for their guitars, and the "70" prefix in the serial number indicates that the guitar was produced in 1968.
Model:
The Epiphone Triumph was a short-lived model produced by Epiphone in the late 1960s. It was a budget-friendly archtop guitar that was available in both acoustic and electric versions. Your guitar is the electric version, which features a single-coil pickup and a rosewood fingerboard.
Value:
The value of your Epiphone Triumph guitar can vary depending on its condition, rarity, and market demand. In general, Epiphone Triumph guitars from this era can range in value from $400 to $800. However, if your guitar is in excellent condition and has original parts, it may be worth even more.
To get a more accurate estimate of the value of your guitar, it's recommended to consult with a guitar expert or a reputable musical instrument dealer. They will be able to assess the condition of your guitar and provide you with a more accurate estimate of its value.