Further to this esoteric discussion:
TENSILE STRENGTH
Grade R = 45-50 tons psi (90000-100000 lbs)
Grade S = 50-55 tons psi (100000-110000 lbs)
Grade 8.8 = 50-55 tons psi (100000-110000 lbs)
Tensile Strength is rated in MPa (Mega Pascow & don't ask me where it came from) and is the load required to pull apart.
Yield Stress is the pressure required to cause permanent deformity.
e.g. A grade 8.8 metric fastener has a tensile strength of 800 MPa that equals approximately116000 lbs psi.
The yield strength is 8 x 10% x 800 or 640 MPa or roughly 90000 lbs psi.
Thus, if Grade R (which is the only BSF grade readily available) has a tensile strength rating of 90M-100M psi we are looking at something less than an ISO Metric 8.8 and probably closer to a SAE Grade 3. (Adjust your torque wrenches accordingly)
As you can see, although these numbers are derived from a different source, they are compatible with Chip's list.
Most new fastener markings are RSB R, CL R or TF R (having just purchased 150 Sterling of them).
Original type fastener markings included GKN R, NEWTON D, SPARTS R & D, WILEY D, BAX D, NEWALL HT, WODEN HT, BEES and CSC R. Do not take these as gospel - they should, however, be a fairly accurate representation of the British fastener markings available at the time of manufacture.
It would be interesting for others to add or delete markings so that we all can end up with an accurate list of original fasteners.
Ed Pohle, Squaw Valley