Serial Numbers are the most accurate method of arriving at an old Hofner's date of manufacture - that is providing it is a Selmer distributed guitar; the European and US market guitars didn't get meaningful serial numbers until 1976.
Alternatively, many early archtops have dates of body manufacture written under the table top, just so as to make it really difficult to read!
Hofner advertised this type of pickup as having "two layer-wound magnetic coils and two permanent magnet-systems".
With the bass unit (513B), the catalogue states that "both magnetic coils are especially dimensioned for perfect re-production of the deep bass frequencies".
All a little tricky if an instant feel for a guitar's age is required!See the picture below of these fairly rare units: It would appear that he "staple" pickup was simply a development from the first Type 511 above, and that the only significant difference is that the non adjustable polepieces ("staples") are now exposed through the pickup casing.As usual, black plastic surrounds were used with the side mounted set-screw location system as in the picture above.You may be able to make an estimate if you can find dates on the control pots, assuming that they are still the originals of course, and if so, were fitted to the guitar soon after their own manufacture.Bear in mind that Hofner made guitar bodies in batches which may not have been assembled into completed guitars for months and sometimes years!This advertising is rather confusing as I can't find anyone who has seen a "Blade" pickup fitted with two coils!More problamatic is that I can't find anyone who can tell me what the difference is between the Type 512 and the 512 pickups, other than the notch on the 6-string 513 version.Later examples however, had a revised mounting to incorporate Gibson style height adjustment screws as in the picture at the top of the page.As an added complication, Hofner introduced a single coil pickup in the late 1960's, which they also called the 511.The first of the "Blade" pickups, this one can be identified from the later 513 6-string unit because it doesn't have a "notch" in the exposed blade magnet.Both the 512B and 513B bass pickups don't seem to have had a notch.