Difficult, who knows what font this is, and where can I find it online? I read about it in the literature of the 1980s.

This should be a long imitation song style, which is often used in general engineering drawing and mechanical drawing. It is also said that this font is influenced by Song Huizong Shoujin style, and it is called "engineering character". When learning mechanical drawing, I usually practice writing this font.

"The fonts used in general architectural drawing are similar to thin gold (imitation of Song Dynasty), commonly known as engineering words. It is the first exercise that freshmen of architectural and civil engineering Department must practice in the drawing course, and it must be practiced at any time. It will be used when they continue to engage in the architectural and civil engineering industry after signing the official documents. " -Wikipedia book entry

This mottled peeling effect on the landlord's picture is generally caused by multiple copies or copies after printing, and the seal is stuck, rather than the special effect of the font itself. See the Chinese font example in the figure below. (not a long imitation of the title, but the following example)