Porsche Racer Car Drawing from the 80's - Copy

Porsche Racer Car Drawing from the 80's - Looks to me to be a copy and not the original. My grandfather was a huge race fan, and I got this out of his house. I have no idea where he got this or what it was for. The car in the drawing is the Porsche 917-30 and the Porsche 956. It is 13 1/4 x 9 1/4 inches. Two technical drawings of iconic Porsche race cars. These cars represent a significant era of Porsche's dominance in sports prototype racing. Not sure what project these were used for, but you will not find anything like this online anywhere. Signed by the artist, but I am not sure who it is; see pics of signature. This was done in 1989.