Between 500MHz and 300MHz models, only change the values of three RC networks (two at the top and one at the bottom), the rest is identical for both. However, these RC networks are set according to the BW and to the 1NB7 (ie as a external compensation). Seems that hybrids are pre selected to be as similar as possible, generally they have consecutive serial/batch numbers.
The TELEDYNE relay is only used for 1GHz models, but all the 1NB7-8453s are pin to pin compatible with the 1NB7-8477s, and with the same functionality. Additionally is possible modify the input stage to allow the use the TELEDYNE relay with the 1NB7-8453 (only for 6000 and 7000 boards). On the other hand, is not logical do that, and is not cheap (>220€ four channels).
Well, I just wanted comment all this as a curiosity.
The next board is a DSO5054A, RC networks in red (only top), serial/batch numbers in green.
Cheers.