"SN" is a prefix code that identifies the manufacturer of the chip. It is used by Texas Instruments. Other prefix codes identify other manufacturers.
74 is the name of the series of TTL MSI circuits that Texas Instruments began producing in 1964:
https://en.wikipedia.org/wiki/7400_series"H" is the generation of transistor technology within the 74 series.
https://en.wikipedia.org/wiki/Transistor–transistor_logic#Sub-types
The code that identifies the part within the 74 series is 7411 or 74_H_11 for the particular generation of transistor. A SN7411 is a triple, 3-input AND gate, which means that there are three separate AND gates, each having 3 inputs. The gates share a common power supply (V
CC) and ground.
You can look up the different parts in lists like this:
https://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuitsThe part number suffix letters identify the packaging. J refers to a ceramic DIP package; N would be a plastic DIP.
If the package letter is preceded by an A, B, or C, they refer to speed grades. After chips are fabricated on silicon wafers, they are tested and segregated into different "bins" based on their speed: the speed is marked on the package as A, B, or C, or as a number in nanoseconds or megahertz for memories or processors, respectively.
7806 or 7810 are date codes. "Jellybean" (cheap) chips like these do not normally have serial numbers. Instead they carry date and factory codes. The first two digits (or first digit for the National Semiconductor parts: 806 and 808) identify the year and the last two digits are for the week during that year. So 7806 means the 6th week of 1978, around February 8 1978. So it makes sense that all the chips in that box were sold at around the same time, whether from Texas Instruments or from National. The National parts do not have an industry standard part number at all, but only the Burroughs custom number, but since it is the same, you can be sure they are DM74H11J (the equivalent National part number to TI's SN74H11J) as well.
It helps to have a cross-reference table to identify custom-numbered parts. You can get one for Burroughs at
http://www.bitsavers.org/pdf/burroughs/icData/burroughs_IC_crossref.pdf