“Stamped Caution” 1953 first contact story by Raymond Z. Gallun

Thanks to the industrious folks at Project Gutenberg and ManyBooks.net, you can read or download "Stamped Caution,” a novelette penned by American science fiction writer Raymond Z. Gallun (1911-1994). Originally published in the August 1953 issue of Galaxy Science Fiction magazine, the story is a tale of peaceful first contact and cultural exchange between humans and Martians. Here are the opening lines:

TEN MINUTES after the crackup, somebody phoned for the Army. That meant us. The black smoke of the fire, and the oily residues, which were later analyzed, proved the presence of a probable petroleum derivative. The oil was heavily tainted with radioactivity. Most likely it was fuel from the odd, conchlike reaction-motors, the exact principles of which died, as far as we were concerned, with the crash....

I haven’t had a chance to read “Stamped Caution" yet, but Tinkoo Valia of the blog Variety SF rates it a "B".