Yeah many years back we used to joke about how chips with a month of 01 or 52 were suspect. Too many parties that time of year, so the silicon production lines would be staffed by people with hangovers. - Gene Paul wrote: a) BB3500 was an Electronotes favorite around 1975-77. TL072ACP will substitute nicely. b) 7435 = 1974, 35th week of the year. Paul S.