Zeta and Aelle are two entirly different tubesets. The seat post diameter will go a long way to increasing your confidence in the tubeset. Typically, Zeta frames are spec'd with 26.6mm seat posts. Zeta debuted for the 1981 model year. The presence of a Portacatena dropout would corroborate circa 1981-1983. That doesn't look like a standard lug cutout but specifically a 'v', which may relate to the builder. The frame looks nice but if it is Zeta then I don't think it adds a lot of value. Maybe $50 over what you consider to be the value of the components.
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