As someone who is about to start using cheap containers myself I just learned some of what you are asking.
It sounds like you have type 1 plastic which is PET (polyethylene terephthalate).
This is the same plastic used to make soft drink bottles.
It is considered food safe. That being said no plastic is considered food safe once poisonous chemicals have been stored in it. If it is new than no worries.
If you were actually storing the food in the container or using it to brine then the current favorite is Type 2 HDPE (high density polyethylene) since it is even more stable.
For gardening a doubt there is any difference since the food is not in direct contact with plastic and even if it was we are talking about only a few parts per billion difference.
The smell you describe is a common complaint. The link below will give you more info on the different plastics, ways to identify them, and even instructions to get rid of the smell.
Good luck.

Here is a link that might be useful: Plastics explained

Since most of the plastic pots I have are very old and falling apart, I have begun to use the bottoms of 2 litre soda bottles as pots. I just cut off the tops, and slit the bottoms to allow drainage. Works pretty good as long as you don't need large pots.

I cant comment on the smell but know what the numbers are.

I just found this last week when sorting all my recycled tidy cat buckets by the date. They've all been out in the sun and the oldest ones are breaking down easily. That is true for their more recent plastic, as the older dates are a different mix and seem like they'll never break down. (The date change looks to be around the beginning of 2008 for anyone interested using the tidy cat container - everything after that degrades fast).

If your symbol is a circle of numbers from 1-12, then the arrow points to the month and the last two calender year numerals are on either side of the arrow. Sounds like your container was produced in jan, 2004.

I can get away with using the most brittle containers for a yearly tomato plant, if they're not moved much. The sturdier (older plastic composition) tidy cat buckets can be used for hanging by their handles for upside down tomato plants as i will trust the handle not to break as easily as it does for the degraded plastic.

Nobody knows what the bucket once was if i wrap something around it, like black plastic - or any material that looks appealing even. The wrap also keeps the sun off them. I use black plastic because it sort of hides the view of the container in the background. But it also attracts black widow spiders around here (san diego). They love to get under the stuff and can find ample recesses of the bucket's rim to protect their eggs. Theres tons of 'em here, so i always handle the used plastic sheets with gloves. (thats another safety point)

Here is a link that might be useful: garden pigpen