my sticker was long gone and any marker inside long faded away. another way is to date the codes on the transformers. there was a post that showed me how to do this, my 200s turned out to have '68 transformers so probably a '69 amp or so. you'll have to search for the post or maybe one of the Sr. members are watching this post and can tell you, but I think it goeas like eg. 606 843. 606 is a Schumacher transformer, 8 is the last number of the year, in my case '68 but could be 78 or 58. not made in 58, discontinued in the 70's probably a 68. the last two numbers are the week it was made. therefore the 43rd week of 1968. gets you a general idea anyway. oh, look, I just read your post again, you bought it in 73 or 74, this form of dating won't get you any closer, sorry