1934 Washington Quarter Light And Heavy Motto

I noticed no one has yet replied to your question, so in case this will help, here is a link to PCGS's CoinFact page. There's a side by side image that I think could clear up the confusion.

http://m.PCGScoinfacts.com/Coin/Detail/5794

The light motto is mainly way less defined than the other two varieties. If there is some other diagnostic besides the weakness, I don't know if it, sorry.

I hope that's useful, and I didn't want your question to go unanswered.

There is a "light motto", "medium motto" and "heavy motto". For reasons too lengthy to repeat here, these are also referred to as Type of 1932, the Type of 1935 and the Type of 1936, respectively (although all three were used to mint some 1934 quarters).

Both the light and medium mottoes have the lower middle vertex, so you can't use that to distinguish between these two types.

The light motto is the same style motto used on all 1932 quarters, but only a relatively small amount of 1934 quarters were minted with this style and only at the Philadelphia and San Francisco mints (no 1934 Denver light motto coins were minted-so if your coin had a D mint mark it is not a light motto).

Distinguishing between the light and medium mottoes is complicated by the fact that many 1934 quarters exhibit wear making the examination of the details of the motto difficult.

The light motto gets its name from the fact that on 1934 coins it looks worn and "mushy" even on mint state coins.

The medium motto is much more distinct and and the letters are thinner.

If that is not enough, then consider this:
In the light motto, the G of GOD is very close to the O.
In the medium motto, the G and O are more separated.

Also, note the thickness of the 1934 date between the light and medium motto examples.

Light Motto:
http://images.PCGS.com/CoinFacts/83...4509_max.jpg
Medium Motto:
http://images.PCGS.com/CoinFacts/83...4509_max.jpg
Heavy Motto:
http://images.PCGS.com/CoinFacts/24...8852_max.jpg

These are all slabbed examples.