The title says 'Assignment in Eternity' but the cover belongs actually to the 'Gulf' novelette (included in this collection of short stories). Roughly: Avenging angels lend the secret services a helping hand. Actual wings are no job requirement, a perfect memory and high SAT scores are. A Masonic Lodge interpretation is possible. The spliced in linguistic speculations are singularly unconvincing. Does anybody seriously believe that nifty markup languages will create goodness as by higher magic. You do not have to be a program expert to know that java script is an open invitation for all kinds of shenanigans. It starts with unresponsive navigation buttons (sawed off steering wheels). Give anybody an inch of power. There is also a good reason for built in redundancy. Keyword, control bits. Actual footage, pitch is grafted on an extended phonetic alphabet to increase the number of available morphemes. The resulting shorthand, one abstract notion per morpheme, will then speed up thinking. Somewhat facetiously, and God created punched cards to feed hollerith machines.
The card game cipher of the jailhouse inmates is based on gematria. ASCII before its inception. Superciliously, most substitution codes are beyond Big Brother. (Obliquely, if pickpockets were only more interested in immaterial souls.) - The fleecy sky around Lunar City spaceport is a nice touch. The Roman sundial, raised gnomon, would work in a way. Less respectfully, a bird bath with built in time dilation.
How to cope with well intentioned editors(Campbell and Blassingame, Astounding and Scribners respectively) and narrow minded proofreaders . Copernicus, a well known problem. I did not know that the various pen names of Heinlein (Anson MacDonald, Caleb Saunders and others) stood for different pay scales. A conflicting explanation is given in a printed preface. A less known alias is reserved for novels which cannot be fitted into the Future History scheme.
An accidental tourist is snatched into an alternative reality. He soon discovers that he has inherited an envelope with one million dollars. Understandably he is somewhat reluctant to part with it. (Text click for a slightly variant cover.)
The cover is somewhat deceptive (most recruitment posters are). Discussions of alternative life styles are interspersed with espionage episodes. A top notch cyburg, custom tailored for risky and fairly implausible Cold War assignments, tries to fit in socially. Run of the mill task, ovum smuggling. There is no shortage of body cavity searches (it starts with perfunctory check ups and ends with routine organ regeneration, from one rehabilitation clinic to the next - the secret service branch will look after its own - Th.Mann, The Magic Mountain).
Timeline: Coir rope made out of coconut fiber is still mentioned in Heinlein's early story. The only kind of rope the Navy will ever use for self-floating painters. A sufficiently long stretch of rope made out of any other substance will drag a boat down. When polymers (nylon) were still beyond the horizon. A world changed by material sciences. Friday is at home in a world of space elevators. Also gone, lift boys (with or without pillbox caps). - (text click for the poster version, without title overlay)
The big timeline caper. A crafty old codger finds himself at the center of a solar system wide intrigue. The bad guys want to snuff him, the good guys need his unique expertise. The bidding war is intense. Immortality genes or something reasonably close are at stake. There is also a hint of time policing. - More easy to grasp: the walking stick can be transformed instantly into a close combat weapon. Let me pay you back your courtesy in unsheathed steel. A particular hairdo of the heroine and part-time gun moll (Gwen Novak) is not mentioned in the script.
The cover should look vaguely familiar. Hint: and at the beginning was the sound track. Arthur C. Clarke: 2001 A Space Odyssey. A monolith can always pinch-hit for a pitch black door. Minor discrepancy: it is specified in 'Tunnel in the Sky' that no space suits would be required for any of the available safari tours. (text click Arthur C Clarke cover).
Speaking of recycled covers, it does not belong but an old counterfeiting anecdote comes to mind. The printing of Escudo bills was once outsourced to the UK. This opened up fresh venues for counterfeiting. The only thing needed were fake credentials. Technically this could probably be described as a top down approach. Not the point. The mint then asked if the same serial numbers could be used a second time. Affirmative answer. Yes, by all means, use the old plates. Justification, the new bills are destined for the colonies. Hermetically sealed off pools of circulation.