We have a 19 x 23 print of Paul Emile Lecomte's Matin Grumeux which was purchased 30 years ago at a local yard sale in Mt. Carroll, Illinois. The letters SZL appear inside a triangle down in the lower left corner just before the handwritten (pencil) Matin Grumeux. The artists signature appears in pencil in the lower right corner. We had this piece reframed years ago and cannot see the upper right hand corner where the Paris Etching Society mark might be. Can you tell us what the triangle means. We realize that SZL stands for the initials of the printer who was a member of the once popular Etching Society. Any other information would also be greatly appreciated. Value?