Lug cutouts appear to be those of Martelly, a Belgium company started in the 1930s by ex-pro cyclist Eddy Martens and still owned by his faimily. They have made frames for a number of pro teams over the years. Portacatena dropouts should put it circa 1978-1983, though many builders had excess stock after that date.
Edit: BB has April 1980 date code, which fits well with Portacatena era, so frame is probaly circa 1981. Frame appears well made with nice lug thinning, though BB shell is rather plain and there are no tangs on the chainstay bridge. In some aspects it looks high grade but in others it appears mid-range.
Last edited by T-Mar; 01-27-20 at 11:52 AM.