I have a Burleigh Brooks 670 enlarger that I have just aquired. It is very well made and everything seems to be in working order. It came with two negative carriers, one is 35mm and the other is larger and the actual opening is 54mmx69mm and tha distance between the reel teeth holes is 65mmx74mm. Is the carrier for a 6x7 negative? Are model 670 enlargers usually ones that will do up to 6x7?